Leg head works fine in first phase, it kind of depends on which ones you have available to you. IMO the LEG head doesn't do too much since it's only Single Target and during the frost phases you reset the cd completely after stunning the frost walls. For me it was nice to have the LEG chest equipped as it made blur a cd that gets you up to full hp. As for the frost phase another tip is to be standing as near the middle as possible when he swaps sides because if you do, some of the walls can be slightly over the edge to the next place the teleports, giving you free extra soul shards from killing them with your Eye beam (if you direct it onto him and onto the shards)!
As for phase 2 I believe it took around 2 - 2,2 min since IIRC my chaos blades came back from cd before the kill. Legendaries for phase 2 I'd recomment at least the AotHG ring and chest since the add does hit quite a lot. On my kill I remember trying to just kite it out for a bit while waiting for new adds since killing them will give you a lot of your hp back. I ran 4set when I did it is quite a nice dps increase, even though phase 1 isn't a dps race at all.