Frost mage is just great for M+ unless it’s sanguine week. You have a ton of tools to control problematic mobs (dogs in HoA for example) to help the run. The class scales very well into higher keys too because of how the mechanics are in the toolkit.
It took me ~2 weeks to put a light forged Draenei to 205 Ilvl. I completely bypassed LFR and grinded gear and upgrades in korthia and M+. I also lucked into a quick nathria queue for my leggo and used soul ash and money from my main.
With the korthia 200 gear I was sitting around 3-3.5k as front in +2/3s. After leggo and hitting like 225 Ilvl I’m ending runs around 5-5.5k overall with plenty of interrupts and mechanics to boot. I rarely do less than 50% of explosive orbs, for example.
Very easy to play, tons of tools, felt so much better than dk. No real experience on any other classes in M+ seriously.