I know how much you hate it but Celebi also does a good job of checking Ttar. It can force it out with Psong or stall it out indefinitely with Leech Seed + Recover. If you're really scared of letting Ttar get to +4 and murdering you with a crit I guess you could use HP Grass to deal with it. Celebi has a dearth of good options for that 4th slot anyway. Also the aforementioned Steelix wrecks it unless Ttar Fire Blasts, but that means it's either giving up Rest or Roar. Probably Roar, but without Roar it's pretty limited. Charmbreon stalls it indefinitely. If you're really afraid of missing Submissions HP Fighting is always an option, granted the HP and Attack drops are pretty noticeable. Ttar is pretty scary in theory. In practice I think he falters because everything he could switch in on has something to ruin his day.