So hit the 100 cubes items last night, going to try and finish the rest of the objectives now, I managed a solo 56 (or 57.....) Grift, slowly working my way towards that level 60 one, doing the objective where you finish a TX rift in like 3 minutes looks like it's going to be annoying 4 1/2 minutes seems to be the best I can do at the minute :-/
That 3 minutes T10 is probably something you're going to need a group for.