You pop it before you go in and when it breaks, and your health is falling off and your MP is low (I see so many dummies dying with full MP bars, it's infuriating), or you're gonna die, you teleport away, pop heals, eat a kit, potion, until shield and tele is back up so you can take another dive. In and out, in and out. You're supposed to use it for BOTH DPS and barrier. You can walk and chew gum at the same time. It even has a neat little sound when it breaks to let you know to start worrying about getting away, how nice. RPR is awesome. Instead of being attached to what you want, you need to understand the intentions and then use it as intended. It's very useful, just not the way you want.
I understand how you feel, and I too find it puzzling the decisions devs make sometimes, but it's not too out there to where it's not too difficult to see where they're coming from.
You're not "Unskilled", this is a bit more complicated than that? I can't tell you to change how you feel about things or else I'd ask if you've tried abandoning your perceptions and expectations that you've fostered over many years.
But for your enjoyment, you'll do enough in PvP if you make the most with what you're given, if you survive, if you're alive to deal damage, if you're smart and know when to min max engagement/DPS/Health/disengagement. Manage your burst windows and compile all your abilities into an explosive moment that all synergize with each other.
You're gonna be a beast on both RPR and DRK.
And you know what the gigachads say, every job is a DPS if you play it right. Tank is just Blue DPS, Healer is green DPS.
You learn how to use what they give you, you're always going to do more damage on a tank/healer than a DPS that chews crayons.
And guess what, even though the numbers aren't the same as a real DPS, it definitely will feel like you're destroying things.