Literally anything that replaces his w would make him more interesting. As is, it's basically the dullest ability there is. Gives a relatively weak shield and nothing else. Not really a decision of when to use it because really anything will go right through it. There are so many possibilities for it, but I think changing it would mean Shen needs some power taken off somewhere because of the massive benefit he would gain from any w change. The passive and q could certainly be made more interesting, but the w could be replaced with a lot of different options. I just hope they don't overload it by making it a telegraphed but powerful uncontrollable conditional % HP true damage mini game.