I open portals by accident all the time. I imagine opening the last tier will be very finnicky to open in contrast, so not all that controlled as I would have thought. Lots of small portals by accident, biggest portal very hard. Though this is in large parts due to the way I play as melee, i.e. stand my ground and just kill everything, which naturally bunches up the smaller portals. The small portals are also difficult to see among all the mobs and skill effects, so you have to be a little paranoid if you want to avoid those.
Item wise I haven't gotten much from them either, but I'm still in Act 3 normal, so eh.
Molten Strike is really fun so far, never used it before. Not sure what weapon to specialize in yet, but my character is working so far, so I guess I'll push the decision out further.
Forsaken Masters I've found three so far. The Armourmaster's task looks much more sketchy than it is. Basically just run to the exit once you free the spirit, as it'll trigger continuous rockfall. Just run past all the new mobs that spawn.