They can be annoying, but I've seen the following issues with chests, that I'd like to see brought up, and addressed.
1. As you point out - some level 5 & 6 chests take 1 pick to open; more ofen it takes 3-8 picks and about 10 attempts. On rare occasions, I've taken over 100 attempts, breaking 50 or more picks, on a single chest. Since ONLY 100.0 lockpicking skill can open these, could we at least have an "attempt counter" on the level 5 & 6 chests, so that if, say, 20 attempts fail, the 21st attempt automatically succeeds, provided that we don't switch chests during the process? (would only apply to the 100.0 skill to pick chests, when being picked by a character that is already Grandmaster, as to not interfere with skill training)
2. Any insight as to the cause of the "killer level 2 chests"? There is a bug that occurs with Expertly (level 2) map chests, and the paragon chests that contain the level 2 maps. About 5% of the time, one of these chests will go off with a trap several times greater than even a level 6 chest. I personally, with all-70s armor, have taken over 150 points damage on several occasions from a level 2 chest - I've never taken more than 105, with the same armor, from a level 5 or 6, and it is rare that any other chest does more than 80.
