I am Chrisyi37 I previously played for ASU's #1 in innovation and just hit rank 166 on my smurf "Marypoppins" and is writing this guide to commemorate the moment. Currently 34-11 as Garrosh in high masters/gm.

He is a great cc tank, very tanky and decent sustain, his waveclear is abysmal without decimate.

3 worse map worst being in #1
1. Tomb of the Spider Queen: waveclear is trash on a waveclear heavy map, but still can do decent(I would still pick Garrosh in this map)
2. Cursed Hollows: fights not close to any towers in which you can exploit and early game a tank usually needs to be solo lane and hes probably gonna be pushed hard by everyone that's not etc or Muradin.
3. Towers of Doom: waveclear isn't as important on this map but there aren't many ways to approach target without being chunked by poke.

3 better map best being #1
1. Braxis Holdout: Easy flips and 4 man squad so easy stacks. waveclear not as important.
2. Battlefield of Eternity: Can throw people into boss stuns op defense hero. waveclear not as important
3. Dragon Shire: Can get easy flips between mid and bot.

When do you take decimate over Taunt?
When they have 3 melee heroes, then decimate allows you to put a permaslow on them while inputting more damage to their frontline.

Take Taunt when
1. A competitive game in which team coordination actually happens and you do not stack cc.
2. Hypermobile Hero Tracer Genji even Greymane

1. With the Q talent on 1 just whenever you see a potential q target just go for it
2. You do not always have to e/q combo if you see a good flip just use it even though your q is on cd.
3. Don't be afraid to flip a tank, but when you do flip a tank make sure you have your eq combo.
4. When you are against a Chromie with Time Loop if you stand next to the target getting looped and into the fray them right before the ult triggers you can cancel the Chromie ult.
5. try to save your w for finishing blows or when you are low, remember it is 10% of MISSING HEALTH.
6. throwing tanks into their backline and trying to get multiple enemies in a q is also sometimes a good idea.
7. Use q to check bushes when the enemy is missing from the battleground, you cannot tell if there is an enemy inside the bush unless the q talent on 1 is not finished, this should at least scare them away.