And not even all the skills. The most both definitely need are the provokes (Provoke, Taunt, Disorient and Accomplice) and Intimidate as a trait. Other than that they're mostly free to use their own class skills for the most part. Both Gladiator and Marauder have a decent number of native enmity generating abilities.

Honestly I'd say:

Marauder = Multi-target tank
Gladiator = Single target tank