It is the fault of the LS and the raid leader just as much as it is the game mechanics.

It is undoubtedly easier to take 4-5 Lancers who can stand around out of Sear range than it is to take other melee who must either dance in and out of Sear (not impossible, but takes time/practice/training) or soak up curative effort (self-cures, healers' mp) which a Lancer can simply "not do" as long as they don't stand close enough.

Archer could always be untouched by Sear, but runs the risk of being locked up (more so) by the ground moves. A good Archer, on the other hand, could still dodge and build TP (yup, with punches) avoid Sear and do great spike damage if any LS/Raid Leader was willing to give them the chance to gain that skill.

The mechanics do favor 1 particular class more than another, but really it's bad leadership to make your allies stand on the sidelines while you plow through a fight in easy mode. If you're just learning the fight, then yes maybe you should stick to easy mode - but once you are winning consistently, it's time to get your other LS members involved. It's a fun fight and everyone can pull their weight in there as long as they learn to dodge effectively, including Archers and Pugilists.

My name is Shai Hulud and I take Archers & Pugilists. ^^
(Prefer Lancer, though, if you got it leveled!)