There are a few ways to tell for sure if an individual used a jump potion. Two of the most obvious ones are:
--Full 260 Shire + weapon + 1 245 Filibuster Ring
--Receives Mapping Achievement upon reaching final boss
Jump potions do not give completion bonuses for dungeons. So if you look at other party members, see multiple 50s, 60s, or 70s for two, and one 60 for one, and there's a bonus message, chances are the one with a singular 60 jumped. Also, if it's an individual like tank or healer, they are probably unfamiliar with dungeon/boss mechanics, and that will be glaringly obvious compared to if the jumper is a DPS.
I highly doubt this tank was a bot. More than likely, they were just ignoring chat. Perhaps that sounds jaded, but maybe that's because a lot of people ignore chat, and ignore advice given, even when it's given in the most friendly of ways. This has been my experience with potion users and non-users. Can't help those who don't want to be (or refused to be) helped, sadly.
I don't think it's limited to just those who used potions. Bad players will be bad, potion or no potion. The fact that people complain about Royal Menagerie and demand that it be nerfed, even though every mechanic present in that fight has been used throughout this entire game, and in 70 levels they should have learned how to dodge basic AOEs but seemingly can't, is testament to that.
(Unrelated, but also: your sig makes me happy. ;_; SJ love. <3)
