lets see
been awhile since updated but i'll try keep it relevant with changes so the swarm of new players can improve their awareness of what they are getting into a little before they are over committed. Main thing to have changed is target cap being slightly more than previously.
This is aimed at large scale orvr mostly, but i can give some side info too...
Tanks
Kotbs despite nerfs still solid, you want one in every party... improved 15% healing for team, buff bot and good CC whilst being fairly tanky... its a core class for any warband... ideally want 4 of these, (1 2hander if high enough renown/gear/experienced... you want all tanks to be SNB beside the one 2hander knight, two handers will generally melt fast in orvr and become a liability in large scale and require too much healing and not enough tanking)
Second choice for tanks
Swordmaster compliments Kotbs the best (its not that IB is bad, its just different flavour and excels more in smaller scale(although all tanks good in small scale) Ideally 3 of these
IB
Ironbreaker is more niche, and has some issues it takes awhile to get good (high renown/gear to over come its "shortcomings" it has bad chance to be crit as a tank to begin with... low iniative, you need to invest renown and talismans to counter act this or you are a liability tank taking way too much damage... futile strikes + ini can help cover shortcomings to begin with, but these points spent, compared to other tanks which can put more into wounds and evasion... means you need to wait until around rr 60+ atleast before they start to even out
Ideally you have one of these...
General
in total you want 8 tanks in warband... its not end of world if you have extra knights that is also a thing but its a bit limited... more morale bomb power BUT you are going to be drained by marauder so this is not a thing in open field and fight is over before you get to that point... if you ever get to that point... at the end of the day if you have 8 ib's... its better than 0 tanks... but you should be looking to balance your parties and pairing knights with sm or ib...
you want SM (whispering wind with slayers btw... put IB with white lion or WH and not slayer (ib can still buff slayer out of party with oathfriend, or just leave oathfriend on a tank at the front to generate resources faster)
Healers
Warrior priests... they are the core healer of warband... you want atleast 4 of these one per a party... your aoe healer and tanky too... you can even have 8 wp and it not be the end of world as they are better to stack than any other healer
Rune priests... these compliment WP's alot, more mobile anti burst healer... good to have 3 of these, moderate survial
Archmage... it really depends on your style alot with warband setup BUT AM is good in the right hands and situations... the issue is not many AM's are that good (its no offence to them its just harsh reality and truth) because AM is the most squishiest healer so if it gets caught with bad positioning or very focussed ... it needs to run away and cant hold its ground that easy compared to a WP or RP which can handle a minor mistake in positioning... AM is unforgiving and a dead healer is a useless healer... (if you stack alot of AM's... you get alot of puddles and can kite alot more as a wb... but in proper direct fights, AM is going to fold faster than other healers... unless super experienced AM (high gear/renown/skill) so you want atleast 1... (2 is not the end of world either... but if you have 3-4-5-6-7-8 your healers will die easy and then no heals, stuck rezzing others will die and fold warband... unless you are perma kiting purely ranged warband)
General
In total you want 8 pure healers... no dps healers, they are junk in large scale and been nerfed recently too... (dps am is good for solo... but very niche dps healers)
DPS is more tricky for order... destro has better synergy and blend basically
RDPS
Bright wizard... Order has one king of dps to rule them all and that is bright wizard
it is the best damage dealer in the game with raw damage and procs and its ranged... but it needs support to make function properly
you want atleast minimum of 4 in any warband for aoe pressure... (you could run full 8 bw but it will be lacking utility... good for zerg busting, not as good for 24v24 unless you start hot)
Shadow warrior... I don't want to hurt anybodies feelings but they are what they are... the MEME class, the unloved underperforming class because it cannot compete with a bright wizard or slayer or even white lion... only reason to play one is if you are a high elf roleplayer and even then why wouldn't you pick a swordmaster or white lion much better choice... maybe one day they get some love and won't be the meme, there are a handful of good ones but for every good one there is atleast 20 bad ones and that is orders problem as a realm bringing useless classes to ORVR and expecting better results.
Engineer... this is the jack of all trades kinda class... it needs to stack balistic skill and weapon skill, it also needs to stand still near its turret (which is easy to kill) for damage buff... where BW can do way more damage on the move and has better morale too(and only needs intel/wounds)... Engi is not bad its not amazing either, its good for utility... and a role if you are magnet engi and know how to pull enemy groups to their death... but too often or not too many engi's just granting free crowd control immunity to enemy without a care in the world and thus shoot themself in foot. For defensive sieges or offensive sieges to break funnels they can be useful... but open field fights its a bit harder for them to pull their own weight in comparision to other classes because other classes mechanics are more suited to this. It does alot of fluff damage, and not so much real damage/pressure. Good to have a couple for realm (forts/keeps) but overstacking them is very diminished returns.
MDPS
Slayer... a unguarded lowbie slayer is useless and dead weight... but a high geared/renown... guarded, supported slayer is very strong... this brings different kind of damage and utlity to your wb, good to have one, and multiple is also pretty good... rampage will make destro want you nerfed, shatter limbs nice utility too.. lacks real morale dmg though... needs to be played on edge with proper support for maximum gains
White lion... this is more a small scale hero than large scale because its lack of aoe compared to slayer/bw... but its okay if you have some ST assist train in your wb (not too much, you want to be predominately AOE optimised for large scale) also WL needs brain on who to pull with pet, who and when to pounce etc... not go chasing away from warband doing own thing being a liability and useless that is no good for anyone. One is not end of world, or two if you are lacking superior choices from BW/SL
WH... very niche class, i would only really recommend one maximum... it kinda has a place if played to a high level/gear/renown but it really needs to over perform compared to a average BW or SL.
Some of the classes which don't perform as well in large scale, tend to do better in small scale... WL/WH... SL is good in both... BW is great in large scale, easy pickings for enemy melee train in proper small scale so that is a trade off...
Anyways hope that helps some new players get some more of a clue where their class is at for large scale.
Good luck have fun
Also orders issue of the past is too high elf / Engi roleplay (not digging at anyone btw just faction wide problem compared to destro)... by that i mean order bringing a spoon to a gun fight and have a realm wide problem of balance... with hardly enough tanks to go around... a insane amount of ranged dps... it meant destro melee train ate them for breakfast over and over in open field (as destro easier to blend) and order was definately not playing to its strengths as a realm
If you want to roleplay as a realm... empire is the best race to roleplay as core wb of bw/knights/wp will be much better than general pug that hits like a wet noodle.
But to each their own... if everybody wants to play dps AM's, sw's,engis thats your choices... sitting on wall and melee dps like slayers/wl/wh going unguarded and thus being very ineffective without balance/support they require to function properly. Play the game as you want, but if you want better results the above will help you be more competitive.