First off don't use ogre as a base for anything.
Secondly being able to destroy a base by attrition is stupid and pointless. Its a neat idea, but it doesn't work for ID.
Lol.
What's the attack rate for pirate? 1 every 1.5 seconds or 2? That's still the same damage lost for the duration, roughly.
Makrura? 45 damage megas, but more than one attack a second (I think)? Still the same lost, I think. It seems like all towers do the same DPS, and thus will lose the same amount of hp, and regenerate the same amount.
Roughly.