How about letting his rockets hit same target more than once (if only 1 target is around, all 3 rockets hit them, w/ decrease in damage for each add'l rocket hit). And change UPGRADE to:
All active Evolution Turrets are healed for 100% of their maximum health and also fire 20/25/30% movement-slowing frost shots (prioritizing enemy champs) for 10 seconds. Additionally, CH-1 Concussion Grenade stuns everyone it hits, and micro-rockets target enemy champs.
These minor tweaks would make people pay for 1 v 1 fights with you, and his Ultimate would actually allow him to deal some damage in team fights.