Nah, here's the trick to it.
Kel'thuzad does his bullshit when he loses the last of his armor.
However, anytime before that you're free to build up a huge board.
The best card for this is Cult Master, which let's you recycle your little guys and tokens into more cards and "combo" pieces.
What you're looking for are:
Echoing Ooze + Blessing of Might/Kings
Argent Squire + Argent Protector + Blood Knight
Echoing Ooze + Echoing Ooze + Defender of Argus
Remember that he'll Twisting Nether against a superior board at 8 mana, so you'll have to wait it out, then drop your game winners and just go for the face.