Champions work a lot better with mobility gear, like teleport ring, +tp on kill, or -mv cost.
The nerf hit them hard, but Balan or Lanval can tank just a well as Mordred with defensive stance while dealing more AoE damage that scale on kill.
Balan has great damage and Lanval has stun+taunt.
I don't bother with defenders except when I need to bring mordred(act 3, very hard).
Vanguards are great, but only for single target damage, and they cannot tank at all.
Mordred murders things in my game. Lightning, Chain Lightning, Charge. He also gets that heal on attack skill that Champions don't get. With +AP gear, he is the Energiser bunny.
I was very disappointed in Mordred, but now that I got to items(armor and sword) that provide %damage on missing vitality, I will see how well he fares (it should roughly double his damage if I can keep him at 30% VP).
On a side note, I hate that the game encourages you to swap titles every turn (like, Court chandler: get + relic on Merchant with Sir Bors, then - build points on constructions with Sir Brunor, then to get a discount on items with Sir Yvain...).
Granted, it is pretty minor, but still it feels like I am gimping myself by not using extreme tedium.