This sounds like a pretty decent team; I just have a couple concerns that might make it a bit better.
I almost feel as if you are trying to have way too many grass types to try to force sunny day to work. The reason heatran is used a lot is because it literally resists every type that is super effective against grasses. I would almost recommend heatran over houndoom, but i think houndoom is fine in and of itself. Still, i'd test heatran over houndoom for a bit just to see how well it works. I would highly recommend taking out tangrowth and putting in a physical wall who has a bunch of resistances to stuff that is super effective against grass. I'd put something like swampert over tangrowth, although certainly other pokemon can fit the bill as well; it was just the first thing that comes to mind, considering literally everything else on this team resists grass. finally, i'd highly recommend getting a bit more diverse with the moves you use, because you really aren't getting that much type coverage as-is. Still, since you are apparently near the top on shoddy, im sure you can think of easy ways to do that.
All in all, i never really like sunny day teams, but i guess this seems fine. Still, you don't have anything that can pursuit or take out pretty much any latias besides just exploding on it; you have no moves that are super effective against it besides on houndoom, but no one in their right mind is switching latias in on houndoom, and latias kills houndoom with surf in one on one due to latias outspeeding. That's about all i gotta say. Good luck with this team, and hope my criticisms helped!