An Otyugh doesn't self-destruct if its stats are higher than 3|8. The +15 HP limits the number of times the skill can be used.
You don't misplay shard of focus, do you ? If you don't want to use it, just don't. If enemy have no targetable perms, you should be forced to destroy your own to get +15hp, otherwise it's plain unfair and stupid.
Zanz would also have to change abilities of cards on field...say you accidentally click an effect and then don't want to use it...you lose the quantum which is the tough part.
Back on topic: the shard should have an element requirement to use its effect. Cards that are big hit and miss (it is one hp, so it could die on your opponents next turn, but if it stays on, it becomes OP) need nerfed to where the game is more reasonable. Those super good effects should be left to luck (mutations on monsters) and one play cards (like destroy) rather than having a monster card that can have it, in this case SoF, so you can have it multiple times.