Actually, the total damage is portrayed by an exponential curve, with the max damage coming out at around 100, no matter your HP, and as the damage approaches 100 it gets slower and slower. For example, a 5000 HP'd catapult target does 98 damage, while a 1000 HP'd catapultee does 91. If you could get 8 titans on the board, that would be 80 damage, and if you froze it, it would be 120. You can see here that it would be smarter to just let titans attack once their HP adds less than 8 damage to the catapult, so for 8 titans, it is smarter to chimera and freeze 4 of them, and then let the other 4 attack normally, giving you 132 damage. Take into consideration that a 5000 HP creature would do 147 damage when frozen, so you can see how fast the dropoff is.
EDIT: Kinda ninja'd by tirear.