I'll disagree with ya TienJe
Personally I love ph. I dont see it as much as a crutch for namelocking, since I can namelock fine with mindblast all the time if I wanted to. One of the advantages of ph is it doesnt cast unless it has a target. This means if you can predict where a caster will land on your screen, you can move your mouse there ahead of time, switch to ph, hold down mouse2. Soon as the caster teles within range of your ph, your character will cast right away. Although you can spam mindblast by predicting where your opponent will land, the advantage of using ph is it starts to cast as soon as your opponent teles on your screen, before their cooldown cast animation finishes, even with perfect timing with mindblast, you can lose a few frames time if you tried to do the same with mindblasting someone when they tele under your mouse. This onetime kb 7 frames (@ 65 cast) after your opponent's activeframe from their tele, which is sure to kick in before whatever spell they wanted to followup their tele with, so imo it's more safe to use ph for a defensive technique like this than mindblast.
Also about casting ph through summons, not sure what it is about ph, but I always seem to hit necros or whatever character through them. Ive killed some druids through 5 wolves summoned when they had 1 hp offscreen. I dont know how to explain this except to "feel out" how to aim ph through summons. It can be done. Im fairly comfortable hitting necros offscreen through golem stack.
Of course you can duel fine with just mindblast, but having the understanding of how to use ph is always a great trick to have up your sleve, as long as you dont mind the extra hotkey. That and it's fun to phpk people offscreen.