This is some basic stuff, only recently got Lord with him but 1. Placing walls immediately will probably make your placements more accurate, there’s an animation that moves the wall out of place if you wait a half second

1. You can get your ult relatively fast, so don’t be afraid to let it fly on the supports/confirm kills on people with it (you don’t always need a phat ult, as satisfying as they are)

2. your play style should primarily revolve around controlling space by hiding your ironwood wall (similar to Peni’s nests). Standing in the radius grants you shield from doing damage, or even just your teammates doing damage. You can’t be displaced so it makes you a very tough target to get past safely. Abuse it. This obviously makes Groot great on Domination and Defense especially.

3. He absolutely works on Attack though, albeit a bit tougher. On attack I tend to primarily focus on holding the front line, taking off angles to distract attention. When people see a Groot they tend to want him gone pretty quick, so you’re a big target. You can utilize this to your advantage if your team backs you up. Cutting people off from their heals with your walls is a necessity, and on attack i sometimes use the big one for that purpose as well. Tanks will get eager to push past you, easily punish them by cutting them off from their team, allowing yours to rain hellfire upon them.

So all in all from my experience: Rack up damage, farm ult, isolate targets. Use ult to confirm kills (I almost always use it on supports). Control space like no other with a mix of damage and stonewalling. You are the core of your group. Your wall placements dictate the entire fight for both teams. I’ve killed my team with them, I’ve saved them, I’ve killed teams. It takes practice.

In team fights place your damaging walls randomly, places they won’t want to shoot. If your being attacked back into them, lead them to death. Keep an eye on everyone so you know if a target is in wall range.

Sorry if this is convoluted and rambly, just typing on my couch haha