Yes to all. I think it’s a debuff because you are losing defense and tenacity in exchange for the added buffs
Other reasons is for synergy and game balancing as some toons work better against buffed enemies or debuffed enemies
Sith Marauder hits harder for every debuff, so the more ferocity as a debuff the better. It forces players to use a full SE squad rather than mix and match with other siths like Darth Traya who is harmful to the team.
Jedi Knight Revan is a buff heavy team so it makes sense his opposite counterpart is a debuff heavy team
we don’t have an official dev response on this so it’s anyone’s guess