As a TC member, i voted for the ban of dugtrio for several reasons (and no, even if some are in SIA, we don't vote the same) and i will explain why :
1. First one is that it removes easily some mon which can pursuit (houndoum, drapion, absol) rotom, a top-tier in NU, with a band, sash or scarf. Yet, it can't ohko some mon but with cheap damage, it can do it easily. It works very well against hyper offense but can do the work well against stall by trapping a mid life special tank for example.
2. Second one, to follow what i said, in NU, most poke aren't bulky so, even with a 80 bs atk, it's enough to do damages before dying.
3. Third one and the most important is that this pokemon trap. It's not as powerful than shadow tag from wobbuffet but is unhealthy by itself. As the NU poke are not bulky for the majority contrary to UU or OU, i find it unhealthy to keep it in NU and should be removed to UU a least.
4. Fourth one, and it's in favor of Dug is that this mon is easily breaked by priorities due to its low bulk and weak bs HP.
I also think that removing the arena trap ability from dug should not be considered as the pokemon would become useless.