Personally, I always feel as though Magnezone needs a large Speed investment to be useful outside of trapping Steels. Its able to trap Skarmory and friends regardless of how fast it is, but if it wants to be useful otherwise it really needs to be switching in on one of its several resistances, and hitting "quickly" with a STAB Electric attack. Otherwise it will just get hammered by a strong attack, even from some relatively slow Pokemon. While Magnezone's defenses aren't poor, it definitely can't stand up to hits easily as its few weaknesses are very common (and often paired alongside what it resists too).
That is where my problem is with this set. No Magnet Pull means you aren't trapping Steels, so you need to use Magnezone's other assets. And I think this set pretty much throws them away by dropping a huge potential amount of Speed. Magnezone is in a position where Speed EVs make a lot of difference against strong Pokemon that lie in a very tight Speed range, and losing that is a real worry. I agree with prem, a mention in AC is probably enough imo.
We knew all the answers and we shouted them like anthems