Is it just me or do GRift bosses drop tons of legendaries, not including the legendary gems. I've gotten 2 legendary drops on a GRift boss kill on several occasions. Maybe it's better to start off at GRift level 1 every time and not kill the boss until the timer is almost up so you don't skip levels?
I found T4 Rifts give, on average, more legendaries than the GRift guardians do. I can usually complete my Rift in under 11 minutes, so waiting for the timer to drop under 4 minutes usually wastes more time than it's worth. Now, that being said, If you can't handle torment 4, like I couldn't when this patch hit, I think it's totally worth it. In seasons, when I hit 70, I plan to simply do Grift 1->2->3->4->5 etc. while gearing up.