Gem Usage in Battle

[LDiCesare]

Why would it be a bug? It's the ai gem usage, the ai decides to use it however it wants. If the wiki gives an inaccurate description of how the battle ai works, it's that site which is wrong, not the game which is bugged. It may as well be working as designed for all we know, and it's not an issue once you have done your homework of checking how many gems you actually need before going to battle.