If you had Hastega you would be pretty overleveled.

If you really have trouble with Seymour, a little bit of grinding might not be bad. Judging from your experiences, you seem a little underleveled. Do you happen to have some Teleport Spheres? With those, you can customize Evade & Counter onto your weapons, which makes you automatically dodge all dodgeable attacks (except for counterattacks) which is quite a great help. Besides that, Fire- and Waterstrike weapons can deal severe damage to those robots.