This is not a full batrep, just a rather frustrating game against my buddy's hellcannons again. I've already played two games against this same WoC army and the hellcannons just tarpitted the bejeesus out of me both games (big victories for him both times due to this). Third game, went about the same as first two. I decide to go horde formation with my Saurus, so two units of 40 saurii, with 2 salamander units, a terradon, chameleon unit and slann in temple guard. I run one of my 40 saurii units up the right flank turn 1. He moves up his cannon. I charge his cannon turn 2. Proceed to do 1 wound out of 17 attacks, kills a handler. He kills I think about 4-5 saurus. I think I win this combat but he is unbreakable. His turn 3, battle goes again, I do no wounds (again 17 attacks) he does another 4-5. I lose combat, hold on leadership 8 steadfast. My turn 3, I buff my saurus to become ws 10, initiative 10, I do no wounds on 17 attacks again (his toughness means I need a 6 to wound but I can't roll a 6 to save myself). He kills another 3-4 Saurus. I lose each battle, stand on leadership 8 steadfast. Are you seeing a pattern here?? His Turn 4, combat continues he kills another 3-4 saurus, I do no wounds (down to 12 attacks now since horde formation is torn to shreds). My turn 4, I do no wounds, he kills only 2-3 this time I think. My turn I buff my unit with pha's protection, charge him in the side with two salamanders hoping to help combat with my str 5 guys. I do no wounds he kills the salamanders. Pass both leadership tests again for losing combat. Turn 5 and 6 are pretty tame, I think I get one more handler down and my saurus manage to survive to the end with 5 models left at game end. Ok now I know my rolls were horrible but come on! My 40 saurii horde unit was tarpitted the entire game, did a grand total of 2, count them, 2 wounds! His 205 pt unit held up my 470 pt horde (killing 35 models) and killed 225 pt salmander unit. This one combat cost me the game since I couldn't kill that one cannon. But what can I do?? Three games in a row now his cannon single handedly win him the game. Alright, rant off now.
Skink/Krox unit will should work pretty well against the Hell Cannon. If you have 2 or 3 Krox you can throw a few S6 attacks into it, plus being a mixed unit he can not get stomps on you. Buffed up by a light or life Slann you should make short work of it. Also if you can get in range you might be able to do a couple wounds with posion javs before you chare/get charged.
SanDiegoSurrealist is correct about the no stomps. You can find it in the FAQ. No stomps and not dreaded 13th spell. Because it is a mixed unit.
Another alternative to skrox (although I personally love them) to deal with the helcannon is a scar vet on a cold one with great weapon, dragonhelm, dawnstone and venom of the frog. If the slaan is within 12", I find this guy will slowly grind down the HC over several rounds and any wounds that get through the re-rollable AS can be healed by the life attribute.