You gain max XP by running the highest GR you can run considerably fast and consistently (3-5 minute clears). Bonus XP gear has been nerfed to death and is mostly useless, with some exceptions but those don't apply here. Just gear for max DPS (or max survivability and buffs, if you're the support character in a group, which is what your Cain's character and the guide you linked is about).
And a general note: Quin has sadly left Diablo 3 and is just playing WoW these days, his guides are outdated for the most part as he hasn't touched the game nor his guides in about a year, and some stuff has changed since then. So look for other builds in the build tool and always make sure they're from this current patch.
Thanks for the information regarding the experience gear. I think i might just salvage all this crap then since it seems like the 10% total bonus exp from Cain's/Born's/Leoric's Signet isn't worth it. I don't even really want to do ZDPS, at least not at the moment (stupid hoarder in me is kicking in saying, "What if later?" lol).
It seems that the Inna/Raiment build I'm running now is still good enough to get me to GR 70, which allowed me to unlock Primal Ancient drops and will suffice for the time being to help me gear. I'm also going to follow his other guide for full Raiment GR100 once I get the gear for it and the Dashing Strike T10 God Monk for bounties. Hopefully it will work for T13 as well.
Soon, if not already (not sure who to trust now, Quin was my go-to), we should have some nice 2.6 builds put up which will help keep me updated on changes. I don't know that they are many huge differences in terms of Raiment yet though.
Sad to see that Quin has indeed moved on from Diablo 3 to WoW. I noticed that from his YouTube and the lack of builds put up by him, but I was hoping that it wasn't completely permanent. Monk is by far my favorite class and Quin embodied the Monk in every aspect. R.I.P.
Ok, I tested a GR60 (Torment 13) and it took me just under 7 minutes. The experience bonus in my character stats says that it is reduced by 100% while in a GR. Does that mean I should instead run T13 normal rifts instead for the full bonus?
2nd test on GR60.