In the current meta you need to remember that tempo is king, so you need to start doing stuff right out the gate. You also can’t afford to have your Disintegrate interrupted just whenever, so I highly recommend Unburdened Flight and Obsidian Mettle as your core PvP talents. As your third I default to Scouring Flame. If I don’t think I’ll get much use out of it or if I really need the extra defense, and I’m not going to be stepping on the toes of a warlock partner, I’ll run Dream Catcher. You don’t want to neglect your utility, but don’t get too lost in the sauce and drop your primary pressure from your damage.
In general as a caster against melee you want to remember that you control where they fight. You can drag them around, so you want to be constantly forcing them into bad positions, and by extension forcing their healer into bad positions. On some maps like Blade’s Edge this can be difficult, but generally you want to be kiting them away from both their healer and in a way that keeps them from your healer, and also in a way that keeps them in range of your DPS partner.
As Devastation in specific you need to portion out your Hover usage. As often as possible try to get both offensive and defensive usage out of it. So, instead of panic casting it when you have no Essence for Disintegrate, your empowered spells are 5 seconds off, and your healer is not CC’d, use that time to spam Azure Strike and fish for Essence Burst procs, then cast your Fire Breath, then cast your Eternity Surge, and then use Hover to dash away and start spamming Disintegrate while kiting.
A basic opener might be something like getting a good Deep Breath, into Dragonrage, into Shattering Star, into Eternity Surge and TtS Fire Breath, and then popping Obsidian Scales and going into Disintegrate chaining. If you’re being focused at this point, or just generally taking significant damage, layer Renewing Blaze into this to keep you super offensive. The CD is at its strongest at the beginning of each match and it’s on a short CD, so using it early means it’ll be up again when you need it.
With how strong demon hunters are I recommend saving Landslide to root them primarily, rather than using it to set up Deep Breath. Don’t forget to use Rescue early and often just like Renewing Blaze, and try to use it primarily for the dash. Instead of waiting to use it for the shield when you’re almost dead, use it to get out of dodge and disrupt the enemy melee’s burst before it happens at all. When it comes to Sleep Walk I’d default to using it whenever you’re out of gas otherwise, rather than trying to get it off and then start doing damage.