Finally, the absolute saving grace for this critique, the mothership core! By far my favorite new protoss unit from a design perspective. So long as it can be balanced, I feel like it adds by far the most to the game for Protoss design.
Purify gives Protoss some MUCH needed improvements in their defender's advantage, especially in the PvP matchup. Cannons and forcefields are all well and good, but they do nothing to blink stalkers or colo rushes in PvP, particularly with proxy pylon warp-ins further compounding the problem. As a result, PvP has almost no good defensive/greedy builds like all the other matchups and thus has become incredibly stale.
Even in the other matchups though, I find Protoss has a really weak defenders advantage in the midgame after forcefields start to be circumvented easily (massive units, drops, nydus, air units, etc). Cannons just don't cut it, especially when compared to bunkers which can be loaded/unloaded/stimmed/salvaged or spore/spines which can be transfused and relocated at will. Purify I think will really help to bridge that gap between early defense with cannon/FF and late defense with mothership, defending storms, and army positioning.
Then there is recall. I know this skill has gotten a lot of flak for being pushed into the protoss arsenal so early, but I really really like it from a design perspective. I feel like it can just be balanced by making its energy requirements quite high and or having some kind of negative effect if it is used to compensate.
And what that balance will pay for is an amazing variety of gameplay being opened up for Protoss. People often think of recall as a get-out-of-jail free card, but I just don't see it being used that way once it becomes common place, especially at the high level. For instance, I don't forsee GSL players accidentally pushing too far and having to recall. They are going to be INTENTIONALLY pushing too far in order to put on pressure, or harass, or delay a timing, or whatever else they think of and then recall when their goal is accomplished. It will allow protoss to play pressure styles they've never been able to before in the midgame where before stim or fungals would shut down any movement that wasn't a main fight and end the game prematurely. This means more small skirmishes and NON game ending attacks all throughout the game, which will give more opportunities for good players and better games for spectators. Big win/win in my mind.