Peltasta C3 can keep Armor Break on bosses up with a rather good uptime of 30 seconds out of 40. Which is worth quite a bit in terms of group DPS increase.
That, and you get a 21-target Swashbuckling which is also a very, very nice bonus both in dungeons and grind sessions.
Sure, you could go for more DPS’y options like Cataphract, but unless you’re investing heavily into STR/DEX, your damage output will be completely subpar compared to specialized DPS classes - I mean, you don’t really expect to deal more than a tiny fraction of what a Cannoneer or Wiz3-Ele3 can do.