As an immobile caster near full build, I need Flash, Hourglass, and dedicated peel to survive a dive

Just played a game as Vel'koz at 5 items where the enemy Shyvana always just went balls deep for me, completely invalidating me, because I have no way of escaping or surviving without full summoners and a dedicated peel. She would basically just run down middle lane at 600 MS and ult through my team, without fail, any time we tried to siege.

It took my Flash, Barrier, Hourglass, and Vi for me to just barely survive. Meanwhile, the enemy team wins the 4v3 that ensues with the rest of our team and takes some objectives.

This is stupid as fuck. Please do something to stop monkeys from right clicking immobile casters and killing them in 2-3 seconds, or give casters more tools to deal with juggernauts and tanks. In this specific case, I hit Shyvana with my entire kit at least three times per dive, and only took maybe 50-60% of her health.

Being able to right click an enemy champion and essentially take them out of the game with zero counter play is not healthy.