The problem is by top level there are AoE SoD and SOL effects, and a number of the latter are nasty enough to require higher level purifications.

To make it worse with quicken they can hit you with more than 1 spell a turn. Multiple enemies can achieve the same effect more easily, or even worse if they're all specialised builds.

You could be in a situation of having to drop a death immunity AoE a round, (since it lasts 1 round), and an AoE multi-essence purification. You just can't keep that up for many rounds before it drain's you dry.

Don;t get me wrong there's a need to be careful of overdoing it at low level's, but well there's a reason mass death ward is 7th level and a lot of common conditions can be cured by 5th level or lower spells.