A Nifel Jarl has no problem against small (30-40) numbers of tritons if he's well-equipped (decent armor, regen, gold shield) and can take the first hit before casting Breath of Winter.
Spesifically, I was referring to Seithokna/Norna. I'd rather have them and 10-20 Longdead than a Skratti with (less than) 2 Giants guarding him. Of course, a Skratti can also lead 10 undead, but is it worth taking Jotuns down, then?
Niefel Jarl, on the other hand, shouldn't take any units with him. If they rout, he'll rout. For a SC, that's bad.