What do you mean by hoard limit? There's a hoard cost, but no limit.

For biped spells, the recycle timers can be considered the "mana cost".

For Dragons, hoard is so easy to get, at least after getting to 100, that it isn't really all that much of a cost either.

For the pet charges, I would argue to just remove them completely for all pets using any sort of charge. For those that require hoard, I think that is completely fine, especially for the hatchy pets that give dragon breath abilities. I'm not worried that some pets might come in a dragon version and a biped version and that the Dragon one has a hoard cost and the biped one does not.

From a Lore perspective, one option to make this 'fair' would be for the dragon specific version to do say 25% higher damage. Then we can think of that as the added bonus damage coming from the hoard cost.

But even if that is not considered appropriate by the dev's, I still do not mind the hoard mechanic or those abilities which have a hoard cost. Hoard does also offer passive benefits to armor and I believe also to Dragon breath skill (not 100% certain about that last one).

Changing or removing hoard I would not recommend. For one, there's no point in such a big change at this point in the games' life.

I also would not add mana to biped spells, not without removing all recycle timers. Then the mana pool becomes the "timer". But you would also have to do this for dragons, hoard would become the nearly unlimited mana pool, so crazy unbalanced. Mobs would also all have to get it, and then combat would likely take years to balance and iron out. So, bad idea to talk about adding mana... no thanks.