Wow you have a lot to "up" at this point. IMO from your post this is percentage that I think is affecting your PvPing.
1. Gear - 60%
2. rotation - 20%
3. You "suck" at PvP - 20% (not trolling just read on)
Gear
Currently the main thing that is affecting you in pvp is your gear hands down. Having gear around your level is vital, if everything you have on is from DK (lv. 10-16 zone) except for your weapons which are from Balmoraa (lv.16-20 zone) and you're level 27?!?! What have you been doing, selling everything??? Currently this is what is hindering you from doing anything in pvp, this also explains why level 10's are able to beat you so easily. Right now you should be on equiping every gear that is around your level you find, don't worry about getting the pvp gear, it really isn't worth it until you buy your level 40 gear.
What you should be currently doing is getting yourself geared, period!
Rotation
Once you're geared rotation is also an important aspect as this help you utilize your class as close as you can to it's complete potential. Gear alone will help you get those 3 medals but rotation will turn those 3 medals into 8+ medals. The key is knowing your role and to focus only on that (besides objectives). You want to play as dps then find a rotation that can maximize your dps output depending on your spec. If you're playing arsenal then a lot of your skills are heavy hitters with AoE so try to target as many enemies as possible to maximize your damage but also you generate a lot of heat so don't spam all your abilities at once or you'll be dead in the water.
You "suck" at PvP
Here's the bottom line, you suck at pvp but hey there is good news, you can improve! Skill comes with practice but that doesn't mean you'll benefit from just doing hours of pvping. Any good athlete's know that when you practice (here's the key) with proper form then you'll improve your game. Practicing without proper form will get you no where other then you just wasted hours on it. Ask fellow mercs on what they do in pvp when it comes to gear, rotation, and how they play in the different pvp matches. There is a lot of good data and idea's out there, just ask around. Also try to find a guild with other higher level mercs that do well and do group pvp so you can see what/how they do.