Juggs is still great. Him being weakened does suck, but thats kinda part of who Juggernauts been for the last 10 or so years now. Its not like its bad writing or anything. Juggs (atleast for the past 10 yrs) has been an anti-hero at worse, I cant even remember the last time Juggs was truly a "villian". Because he is more of just a conflicted soul as opposed to a villian, it makes sense that Cyttorak would weaken him at times, like when he was on the X-Men shortly after G. Morrisons run, or like he was in Excalibur. The more noble and "heroic" Juggs is the weaker he becomes. The Only reason Juggs went back to being "bad" was for noble reasons, so he could possibly stop the Hulk, but he had to sacrifice and go cause more destruction. It was only a temporary boost in power though because he didnt stay "bad" for long, eventually the Uni-Power chose him and he "passed". The way Juggs is now as a person, as sad as it is to say this, he should never be as powerful as he's been in the past when he was more of a "true villian".
If some writer, wrote Juggs to be as heroic as he's ever been and also write him to the power level of the Hulk or the Red Hulk, then thats bad writing. Juggs being weaker in Thunderbolts is a sign of good writing and continuity, and anybody who doesnt see that, just dont understand the Juggernaut.
Its like the Hulk being calm as librarian, yet being at his peak strength levels.