What units is it viable to use the Corruption ability against?

Solution 1:

This ability is good against almost everything - just use it on every enemy unit as long as you can. Just make sure to prioritize it - meaning, first corrupt the biggest, higher-hp targets, then the medium-hp ones, then the smaller ones and so on.

Why? Because on the one hand, battles usually do not last longer than the cooldown on corruption, so there's no point saving the ability for later. On the other hand, almost always the down-time between battles - or, alternatively, the time it takes the enemy to rebuild his heavy units - is longer than the time it takes the ability to recharge anyway.

Granted, corrupting individual marauders or phoenixes is pretty silly - but as long as you can, and every bigger unit is already corrupted, why not?