I was meaning to post a set of proposals concerning the SW assault tree, but Dansari just beat me to it, so I won’t need to state why assault tree needs to be looked at as he already has introduced the problem very well. However my proposals are different and I would like to introduce a new methodological approach to the problem:
Imho the focus of this discussion should be how we can make going melee on a SW not only effective per se, but also useful to a group, so that a SW who has chosen to invest mastery points deep into assault stance tree can be a desired member of a party.
ISSUE 1
The assault tree is clearly underdeveloped and lacking compared to the other two: 2 glaring half assed or underperforming abilities stand out: Swift strikes and Sweeping slash.
PROPOSALS
1. Make Swift strikes hit for the improved damage regardless of enemy building an ability (other wise the damage is laughable), + each of these hits that crit will give AP to the group.(BENEFITS THE GROUP)
2. Make Sweeping Slash, probably the most useless ability in any tree any class, apply an armor or initiative or wounds or block/parry debuff. AoE debuff (BENEFITS THE GROUP)
ISSUE 2
Classes that go melee have three choices weaponwise:
2-HANDED big powerful weapons with slow attacks, high AA damage and breakthrough,
DUAL WIELD, which translates into more AAs, more parry etc, and finally
1 HANDED WEAPON + SHIELD, with the obvious defensive bonus of block.
When SWs dive into melee, they have no offhand extra damage and NO BONUS AT ALL, neither offensively nor defensively, not to mention that the idle hand could develop bad habits (i.e nose-picking while in combat, or even genital massaging)

PROPOSAL:
Make assault stance give +10%parry and +50%increased AA speed. In this way SWs can bridge the gap with other mdps and get nearer to what a dual wielder gets automatically and naturally just from being able to wield two 1handed weapons.
This solution doesn’t need any item implementation.
Also note that even with this SW doesn’t get all the possible benefits of dual wield as the bow will contribute stats but not %on hit procs.
This change would be exactly in the same spirit as the way Assault stance works buffing armor from light to medium and turning ballistic into str to allow the SW to be not too far behind melee dps during the moments that he needs to be in melee after switching back to medium or long distance.
ISSUE 3
Acid Arrow, the SW armor debuff skill will only increase to significant levels of effectiveness if points are spent on scout tree. Right now this is not a problem for the typical cookie cutter ranged specs that invest points in skirmish and scout. Assault specced SWs, however, would be forced to spec Assault+scout if they were to really benefit from Acid ArroW.
PROPOSAL
Change Sinister Assault tactic in the following way: instead of allowing BA to ignore all of enemy armor, make BA undefendable and apply a hefty armor debuff, which outshines acid arrow.
The advantages of this are twofold:
1. Assault SW would be more desirable for a group (This ties in with my suggestions about Sweeping Slash and Swift Strikes and would result in assault specced SWs being able to provide a big armor debuff, AoE wounds or initiative debuff and AP restoration to a group)
2. The elite and reliable armor debuff from BA would tempt some ranged SWs to spend some points in assault stance and actually switch to that stance to benefit from the armor debuff. And that is the way SWs were meant to be played.