That one time I played Overwatch with NoobHunter 

Lifeweaver is almost certainly only viable in dive. As many have pointed out his hp/s is nowhere near strong enough to sustain brawl and he provides no significent damage/ utility over something like Baptiste or Zen to work in poke. From what I can tell his main strengths lie in the range and consistency of his heal from his m1 and ult. Whilst appearing small, an unmissable 65 burst hp on a flanker every 1.2 seconds from a support 30m away is no joke and whilst his ult would likely be instantly blown up by an uncontested backline, if it is spawned whilst the enemy backline is being dove upon, it would force dps to chose between focusing tracer/genji or killing the tree, not to even mention the instantaneous 150hp that the dive would receive. His life grip seems most powerful in an aggressive dive where it can be thought of as tracer recall that you can cast on your teammates allowing for divers to blow all their cooldowns on chasing kills with the security of knowing they can be life gripped out. Whilst petal platform has a number of uses for denying ults/ enabling snipers, I believe these are pretty niche and its main usage will be for self peel which is most useful in a dive setting where tanks and dps are too deep to peel for their backline. I can see him working most effectively with Ana as a long distance backline where the ana can provide most of the healing whilst Weaver peels and helps ana reposition with platform whilst healing and gripping overextended divers. Whether or not he is actually strong enough to push dive more into the meta or even strong enough to be ran in dive is yet to be seen, I suspect he will be pretty weak as his numbers seem a bit underwhelming, however I am definitely looking forward to trying him out. Would love to hear other people's thoughts.