If you play a survivable hit and run style army then a squad of assaulting Dire Avengers is worthless. The extra range will keep you out of combat and the 5 extra shots are worth it. By themselves the assault capability is so minor it’s not necessary, and this is especially true if you play a shooty Eldar list with several Dire Avenger squads.
If you play a more in your face, bring the fight to them Eldar list than the extra assault capability is essential and adds a ridiculous level of synergy to your army. The beauty of the combat Dire Avengers paired with an assault Aspect Warrior squad is the capability of dealing with up to three units in one turn. The trick is having your low strength Dire Avengers hold a unit in close combat where everything else you have will simply wipe the enemy and become exposed to rapid/mass fire.
My Howling Banshees can destroy a group of Assault Terminators while my Dire Avengers are blowing away the Tactical Marines standing next to them. I know the fist and the Melta will probably survive so I can attack them and strike at my higher initiative either winning or holding combat. On the next turn, my Banshees will receive cover saves from whoever is shooting through the Dire Avengers. See example below (general illustration).
Here is a real example of this:
My Kit
Eldrad runs in a Wave Serpent with 10 Howling Banshees (Acrobatic, Executioner)
10 Dire Avengers in a Wave Serpent (Bladestorm/Defend; Power Weapon/Shimmershield)
Scenario:
10 Khorne Berzerkers with Kharn the Betrayer
10 Khorne Berzerkers standing nearby
5 Havocs in the distance with 4 Autocannons.
Doom the smaller Berzerker squad without Kharne, Fortune Dire Avengers, Fortune Howling Banshees
Howling Banshees foot stomp the smaller Berzerker squad, but are now standing out in the open (no cover to consolidate into)with their crappy 4+ save just waiting to be lit up by AP4.
Dire Avengers kill most of their target, leaving Kharne with 2 wounds and 3 guys in his squad. Now the Dire Avengers assault Kharne with their crappy S3 but with 3 Power Weapon attacks and at initiative. I put one more wound on Kharne and kill 2 more Berzerkers in the squad, the attacks back are brutal (even with the minus 1) but with the 5+ invul and no Furious Charge I only lose 2 guys and win combat by 1.
On my opponents turn he wants to shoot at my Howling Banshees, but has to shoot through the ongoing combat which gives me a 4+ coversave, that I get to reroll. The next turn the Banshees assault Kharne and take him down.
You can do this same thing with 30 Orc Boys w/PClaw and a squad of Nobs standing nearby, or Genestealers with Guants, Assault Marines with Tac Marine/Fist, etc, etc, etc.
If you'd try that against the tactical squad, and killed 7 marines, I'd just use combat tactics and fall back. leaving you completely exposed. and aim at your banshees. it's a nice plan, that probably works against other armies, but not against combat tactics marines, just so you know :)
Cheers,
Folkert
Your absolutely right, this was just a quick example and there are many variables that change the story based on what other squads are in range and angles of concern. I am just trying to show how I use Dire Avengers to hold troops in combat to give cover saves to more valuable units. A fat stack of Ork Boys/Nobs and Lootas would prob have been a better example.
If you used Combat Tactics I would have to Star Engine the Wave Serpent (and lose its more valuable shooting) for the cover saves and then just keep it within 6″ to walk you off the board.