"Do I stick with my friends and keep trying to motivate them to do better, or do I leave them behind and find myself a new guild with more competitive players?"

It's safe to assume that your guildies don't play, research, and write about this game anywhere near as much as yourself. Stick with your friends, enjoy the top of the meter, and when you have extra time and a receptive player, research how to increase his/her DPS.

But stay with your friends.

I agree with this entirely, along with most of the commenters thus far. The biggest thing that a guild needs is teamwork and cooperation, which you should have plenty of in a guild of such close friends. Your guild-mates may not be as geared or skilled as you are, but they're still going to give you the best experiences. If you were to jump ship to a new guild, not only do you risk alienating your current guild-mates/friends, but you risk finding yourself stuck in a guild with people who you just don't "click" with as well.

In WoW, a lot of the game's best moments are enhanced when you're witnessing those moments with friends.