Decay has it's use. Mainly as a helper to other attackign methods in the same team.
But I still find it lackluster.
How about the follwoing small change.
Add a small amount of Direct Damage (independant to the 50% loss) per level. Much like an E/AXbow. I'd like this (in addition to being tiny) to also ignore armour like the rest of the Decay damage does.
Would give the only front hitting DD a litte extra 'punch', and give it a real reason to train above base, bar protecting itself from AMF.
And finally, Decay could kill. ;)