I've played Shen for a while before switching to Nasus as my main, here are some suggestions i think can work.
First off i agree that the E hitbox needs to be a bit bigger, pre-rework id land taunts left and right now its annoying when you don't land taunt when it should have
Another option i've seen thrown around is to take power out of his ult(make it semi-global?) and putting it back into his basic abilities. An idea i just thought of regarding his ult is what if it consumed a % of Shens HP in compensation for the shield he is giving to an ally? Like maybe 10,15,20% of max or current health? just throwing out some numbers.
Some other changes could be increase the missile speed of his sword as it drags, less energy consumed on Q or E, maybe bring back % damage reduction to his E?
Or to completely throw this out there what if Shens q had either a % heal on empowered autos or % magic pen for a small amount like maybe 5% on empowered Qs?
Either way, im hoping for some Shen changes.