I am a little bit frustrated with the strongboxes myself atm. Yesterday I ripped my one month guy with 5k life and 75% fire resistance at merci docks, when I opened a blue box. I clicked, screen froze for 2 seconds and when it resumed it turned out 20 fire dogs have spawned on top of me and started blasting. It was only a few weeks ago when someone posted a video where they opened a box and 20 devourers spawned, they even used warp and it just desynced them back to box to get oneshot. The main problem is you can open a 1000 boxes and be fine and when you least expect it something completely out of your control is going to happen.
I am concerned about these things getting added fulltime the core game in their current form because at some point I would consider just not opening them ever if there is a 0.1% chance that it will be an insta death, but then again GGG is balancing drop rates accounting for boxes, exiles, etc.. so it gets even more frustrating to think about it.
I don't think the community should justify the obvious technical problems with stongboxes by saying there are ways around them. I am perfectly aware of timing warps, mines and other movement tricks to avoid death by stongbox. But the fact you have to resort to such things in the first place shows there is a problem. And more so these methods are not even 100% effective.
I just hope the devs are sure what they are doing before integrating the boxes in the core game especially in the hardcore leagues.