We are all stuck with Mascots. They are generally not thought much of until you lose them and then you miss them a bit. I will not rave about Flask, but he gets a job done.
For the most part, he hangs out around Vitriol and Mist. I always deploy him right between them so that if they need a speed boost turn 1 he can pop it out there. The biggest downside to his usefulness is that the smoke must be centered on him.
Most of the time I try not to allocate INF to him unless absolutely necessary. Light footed helps him get around. Occasionally, you may need to Sprint. Even less often you may want to take a few hits on a crowded out big guy surrounded by conditioned opponents to trigger Intensify. I that case do not forget that charging may present more wraps than just walking in. I have recently come to value models with low TAC and shorter Playbooks for that reason.
He standard role in my list is to support Vitriol. With him crowding out and popping smoke, he can really turn her on.
His other role, when needed is to shut down the Boars and Rages of the world. He is tough enough to stand up to them without the charges and may just live to talk about it. Its not his optimum role, but nice to have in a tight spot.