If %HP Dmg is for shredding tanks...
Why do nexus and inhib towers not have them? As some who has played Garen and every other Juggernaut out there enough that I KNOW I can sit under laser turret for half a minute and inner and outer turrets for almost as long, even I don't find that fun. At all.
Even adding something like 2% current HP dmg would really help alleviate how stupidly easy diving for a carry's kill is. 4% scaling to 8%/12% over aggro time would actually make it more interesting. If you're going to take armor off turrets next season, at lest make them more of a threat to tanks, else they'll get ran over even more easily than they already do.