Tinker's Warp Flare wouldn't be so weird to use if it gave vision while the enemy is disabled by it
Sometimes when you use Warp Flare and the enemy moves in an unpredictable way, they can be moved to a place where you have no vision or over a cliff and then your team doesn't know what to do to continue the fight correctly and benefit from it.
If Warp Flare granted vision over the enemy while he was affected by the root / cast range / attack range reduction, it could help smooth the use of Warp Flare during team fights, so you could even use the skill more often without griefing your team.