Roll is not bottom tier. Hard to hit, a few decent normals, a killer throw, and Beat Plane chip is just as good as Megaman’s.
Jin is bottom tier because he cannot make anyone make a mistake. The only viable low attack he has is low short, which is the slowest in the game, so you can block high most of the time with no problems. As long as you don’t get ballsy and try to challenge Jin’s air-to-ground priority, you shouldn’t get hit by anything worth worrying about.
I used to think Morrigan was the worst, but since she can triangle jump she can at least have a mixup game (for 25% damage each time, but hey). So bottom tier is made up of Orange Hulk (can’t do damage easily and takes it bitchily, and is also huge and has a low superjump) and Jin.