I've always kinda liked Dire Avengers. But when they got nerfed and the range of their Shuriken Catapult dropped to 12" in 3rd edition...they hit the shelf for a LONG time. The 4th Edition codex saw the range of their Shuriken cats extend to 18". Still shorter than marines bolter of 24", but a huge improvement.
Another change was the ability of the Exarch to "Bladestorm"...a skill that allows all shuriken cats in the unit to fire one extra shot in the fire phase. Going from 22 shots to 33 shots is kinda handy when a unti of orcs is about to charge yah. Downside is you don't get to shoot the next turn...but chances are you will be in hand to hand anyway.
I only had a small unit of 5 Dire Avengers painted up, back from 2nd edition when they came only in units of 5. So with the new Troop being necessary, I had to increase the numbers of this unit. The tell tale item that makes a Dire Avenger is the roman style headdress on the helmet. Going through some of my older minis, I had a bunch of the very old Eldar Guardian figs that had a roman headdress on their helmets. So little dip in some Pine Sol to strip the paint, some time of the workbench...and I have a full squad of 10 Dire Avengers.