Ah sorry, I went over it in a hurry, didn't notice Magic Weapon. Then use Black Hole - Spellsteal instead. Again, as I said, you get 150% attack speed or so through all your Archon stacks, so the 10% IAS from Slow Time are kinda "meh". Black Hole is great though because it instantly seems to give me tons of Obsidian procs to get Archon back up (again, we're talking speed farming here).
I think it also depends a lot what you want to do. T13? Bounties? GR70s? GR80s? GR90s? Solo, in group? Play with CoE or Obsidian? Play with Hydra or without? There's a ton of variants and I honestly have no idea what's "best", I just play what I prefer. Also, almost every single guide I've seen has a mistake (and I'm quite sure that if I were to write a guide I'd make mistakes as well). Despite so many people playing MH wizards and so many variants and so many guides, there's still a lot of question marks. So basically try out a few builds and play whatever you prefer. The build I described is what I run on T13 and up to GR80s (with In-Geom and Obsidian). I prefer it over the CoE build which obviously isn't very suitable for speed farming. But I'm sure others work as well.