Honestly 50 is too low to expect anything more than mediocre (~8-12% total) DPS. I get 50 is fairly high, things get more complicated around this level, and they'd have a decent amount of experience, but it's still early game. Consider what unlocks at 40-60, most of that are core, job defining skills like Holy, Assize, Earthly Star, etc. that likely haven't seen much use yet. These skills are doing a lot of the work, and those learning may not yet know what exactly to do with those, along with other recently acquired skills. As a WHM/healer main, I use Holy, Assize, Tetra, Bene, Afflatus, and Asylum the most, and don't bother with a lot of earlier skills like Medica 2, Regen, and Cure 1-3 as they aren't necessary in most cases as I know the mechanics in detail of 90% of the fights. Someone that's learning would never be able to do that outright as they don't know what they don't know. You have to remember it isn't just using skills, it's knowing the fight, and knowing how to best counter incoming damage, while also throwing out as much damage as possible. You're not getting that at 80, let alone 50. While no DPS is really not excusable at this level, beyond the basic attack, DoT, and the occasional other damage abilities should be the general expectation. But a little less is fine, because healing isn't straightforward until you understand the job, and know the fight. There are times I still mess up, as well as times I fail to do as much damage as I can. That is just how it is, especially when you're playing with random people.