So Cartography and esp GM Carto would be a factor as to loot quality of chests then. So you cannot stone carto and then dig and expect to get top possible loot. Looks like you could stone RT and sustain the consequences of that (more blue guardians with no loot, more fire blasts, longer time to actually open chest), and would need to keep LP for the high level chests-last 2 levels. Another choice would be to keep RT to a middle ground level like 60-70, carto 100, LP 100. Then formulate your spec around that, be it tamer or Mys. SW, Mage etc. Tamer probably the best for high levels with 5 slot pet like trained beetle, then you would need to isolate the spawned guardians divide and conquer, other pets may be self-healing pets or combo types healer/high resist pets, or even Naja with high resist spells, resist poison, armed with FzWW and you will need to heal Naja.
Many ideas and combos to try. Looks also whatever you do, you need some luck according to some well-respected testers, some people use the word "sweet spot of 1500, 1300", others go for max luck, 2000, or even 4000 or as high as attainable, that MUST be there as soon as you start digging the ground, before the box spawns and probably during the spawning process for the box. Then after it has spawned you also get the blue "guardians" 1,2,3 depending etc. Move away quickly, hopefully mounted or gargie speed, switch suit instantly, now possible in both CC and EC, with hotkey, into your fighting suit, and get after the blue guardians. After the box is in the open, presumably luck is not needed if I understand correctly. Then after you kill blue guardians you use the RT on the box etc.
Also looks from what the Devs have let us know, luck is important to hope for decent loot.
For tamer, I would suspect you will also need real taming 120, real lore 120 to use the masteries III to its fullest benefit to keep the pet alive with esp. paragon spawn or multiple GD, AW etc. if you cannot separate the spawn in time.
With some of the spawn it may be way hard to keep pet alive with anything, or may take extremely long to eliminate if counting for the pet or something like EV,s to do all the fighting fo you. This is where additional skills may be needed, like Mys, SW etc.
Also Davie locker=priceless, I would dare say indispensable.
This treasure hunting is an interesting challenge, and will create some new specs of templates.
I have used gargie MYS/SW with no deaths whatsoever, but have not tested last 2 levels yet due mostly to time constraints with RL, but will definitely give it a try, but need first to get luck suit up to like 1500 or so without the statue. Fel. is my favorite place, and always looking for Fel maps.