If I had a clear enough memory I would post reports, but this is what I recall.
Match 1: Black Templar.
land raider with 8 assault termies
Lasback with 5 marines, one of which also had a lascannon
2 rhinos with crusader squads, 1 with Emp champ, the other with an HQ that had the 'holy hand grenade'
Pretty much was able to just use my mobility against him. I am blanking on exactly what he killed, but I know he went after my prisms as priority, especially after an unfocused, 2-prism shot wiped an entire crusade squad, leaving his HQ to be mopped up by dragons.
Match 2: Different Black templar player.
he used 5 lasbacks each with around 6-7 marines in them and an emp champ in one
Drop pod with other HQ and a bunch of crusaders
This match was much tougher, and though he made a big effort to kill my prisms, cover + bad dice roll on his part saved them, losing only 1 by games end.
Match 3: Grey Knights ( and the guy that went on to take 1st)
2 auto dreads with psy ammo
2 assualtbacks with psy ammo and some knights with that weapon that can switch between assault or heavy.
one of those carried a tech marine
1 rhino with inquisitor and some more Knights.
Vindicare Assassin
He stole initiative and Alphaed 2 prisms, 1 exploded by the assassin and one lost its gun to the dread. The remaining prism hid from the dreads and assassin while picking off knights with the focused beam (managed to clump one group up and taking out six of his guys with one focused shot, including the inquisitor)
Game 4: Footdar
Eldrad
3 fully tooled 8 man harlequin squads
2 Pathfinder squads
2 Sniper lords
He wanted to kill the prisms, but really did not have the firepower. He only got 1 with the lords and his harlequins were never able to effect the game.
In the end, my avengers got out on a few occasions, and only when i knew they were safe, so their flimsiness was never an issue. In addition I only ever lost avenger transports in game 2. The dragons, while few in number, made up for their points in almost every game, especially against the 2 templar players. The threat posed by the prisms, and the fact that i kept them covered as best I could, probably helped as most people could not dedicate enough shots to my troop transports.