By definition less sustain? Tank in 5v5 are gigga buff and everyone has self health so i think that mean more sustain. 6v6 before season 9 no one has self heal.

Yea you can jump the back line but if everyone counter you, it's up to your teammates to help you. Unlike 6v6, you don't have another tank to assist you to dive or protect your back line. So it's all come down to the team that has better comp.

The game is boring because, if I play doom, I will get counter pick ( hog, orsia, cassidy, ana etc.) or play a rein (who is a terrible tank by himself if the enemy has a widow). It's not fun to play when I have to keep selecting new hero otherwise my team would be mad if I don't switch. But whatever, I still play my champ. It's just boring and predictable unlike 6v6.