less expensive: 5 points less without upgrade, which wastes poison
poison: 1 shot/model. core and special skinks are better even if you have to wait one round more
drop rocks: nice, but if you wanna kill something rippers are better
no frenzy: yeah, but no ITP too then. Rippers frenzy is avoidable turning them away from the opponent and they won't panic because of ranged attacks thanks to their frenzy.
I think terradons' time is over. If they were ambushers, if drop rocks was not one use only, if they had some massive penalty to hit them with ranged attacks or protection of some sort, if terradon was a mount option for priests (or even saurus heroes), then terradons could be worth. But as they are now they only try to fill roles better filled by chamos and rippers.
An example of a rule which would have made them interesting:
-grab enemies: after dropping rocks once, in the remaining movements phase, terradons have to get new ammo. Every terradon in a unit which flies over an enemy unit can try to grab a single infantry or cavalry model and fly away grasping him with claws. Terradons have to roll to hit to grab opponents, but they don't have to wound. Armor saves and regeneration are not allowed against "grab enemies" (terradons don't kill enemies, gravity will kill them instead), but ward saves are allowed as usually. Terradons add +1 to their to hit roll if they target an enemy unit which is engaged in close combat (enemies focus their attenction on the fight) or if they target a solitary model. "Grab enemies" can target monstrous cavalry or infantry or warbeasts, but if this is the case you can target one enemy model for each couple of terradons, rounding down (for example 5 terradons can grab 2 trolls). Roll once for each couple. Terradons can even grab heavy targets like monsters, chariots or warmachines but they have to be at least 4: roll once for the formation. ONce a model has been grabbed it's removed as a casualty: terradons drop him on the ground before landing or heavily land still holding the enemy in their claws. Terradons can drop the screaming creature on his comrades' heads: it works like drop rocks, with the following differences: infantry causes D3 hits, cavalry 2D3, monstrous cavalry and monstrous infantry 2D6, monsters 4D6. The strenght is equal to the grabbed enemy's toughness+D3 to represent the weight of his body and the acceleration caused by gravity. Terradons can grab a single model, even a character in a unit, but a character is still allowed to have a look out sir. "grab enemies" cannot target swarms.
make terradons cost 50 points each and it's done.
couple with tiktaq'to giving his WS to his unit and an additional +1 to hit and you have a reason to field him
probably it's not balanced, but i wrote it in 5 minutes while vetock had months to write the book, so he could have found a way to make terradons useful. But he didn't, so rippers are the way.
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