I took my level 6 ranger with light armor into Shaag's Helmet (or whatever it's called) on elite (that made it level 5). I got two champions (both melee types). They were doing between 10 and 20 hp per attack. About double the 1 to 10 of the normal fighter types. I quit before the end because this was right before guild night for me and I wasn't going to make the group wait while I finished a test.
The Guild did a gianthold quest on elite. We got several champions but not together. I wasn't able to track the damage as well but we didn't have any deaths. The party was levels 14 through 17. Tactics were simple. Hit the nastiest guys first, and keep hitting 'till they fell. We had a good healer with us.
After the official adventure, two of us (me with level 16 rogue, and my friend with level 14 rogue) got a couple of hirelings (level 14 healer, level 16 fighter) and went into Mired in Kobolds on elite (making it level 15). There were several champions but we only saw them show up singly or in pairs. Being rogues, we used smart rogue tactics. We set the fighter and healer back, sneak up and use bluff to draw the kobolds back to us one at a time and take them out. This worked well.
The champions were hitting me for somewhere around 50 to 75 hp a shot (when they got through AC and dodge). We only ran into one champion caster and while I had aggro I was hiding behind a wall, so I don't know what the damage was like. By the time the rest of the group got aggro, he was almost dead. So I can't comment on champion caster damage.
Note that both my characters have pretty good gear for their level (not uber, but lots of named items and raid items). This very limited test indicates to me that the elite champions should not be made any weaker than they already are (in my opinion).