So many answers.
I was surprised that some people recommend the buzz because the roc is supposedly too stable. I find the z buzz and z comet to be more stable than the dx rancho roc. I hear the x comet is not so stable, and I'd try that if I weren't already used to the dx stingray, dx roc, and dx whippet as my midrange discs. But I'm not going to comment further on any discs I'm not familiar with.
I have to say I like the star mako. It's similar to the coyote but straighter, and Blake says it starts out like a roc that has been beat in for 6 months. I find it is the same straight line as the roc but with a much slower fade than a new roc. I think it would be a really friendly disc for a beginner. But I'm sticking with the dx rancho roc for now because it is really punishing me whenever my technique is just a little off, and I like that since I am practicing daily and trying to eliminate error.
I suggest getting a few dx rancho rocs and practicing driving with them, and there are a lot of top pros who say that again and again. But also practive driving your putter, especially in strong tailwinds, or drive a really understable midrange in tailwinds, like the dx stingray. But your dart is almost a stingray already, so I think you are set for an understable all purpose disc.
For strong headwinds, a severely overstable high speed disc, like a firebird, is needed. For more moderate headwinds, I like a bit slower, bit less overstable disc, like the banshee.
I like to address strong crosswinds using a severely overstable low speed disc with a lot of turn resistance and fade, like the whippet or banshee, and throw then so they try to fade into the wind (i.e., rhbh into a left to right cross wind, rhfh into a right to left cross wind) and wind up finishing long and straight as a result.
So, long story short, to drive straight in various wind conditions, you might consider:
Strong Headwinds: Champ Firebird in Max Weight
Moderate Headwinds: Banshee
Strong Crosswinds: Whippet or Viper
Strong Tailwinds: Dart or Stingray
Little or No Wind: DX Rancho Roc or Star Mako
Once a roc beats in to the point it starts flipping, it can be used in place of the stingray. Then I can start carrying rocs in different stages of wear to fill those same slots.