If pure tanking power is tanking into account, this thing is second to none. Just like Rock Elementals, the Gasbags has a 80% damage reduction from almost everything (as long as it is at least partly inflated). The Gasbags, however, is much easier to tame, can be bred and has a saddle which is not that hard to find at all. Their smaller hitbox is welcome when using Velonasaurs and guns from behind them as well.
The only downside is their low damage, and also that they can't damage stone (and turrets), so don't expect to raid entire bases with it alone.
When damaged, a bit of gas will escape, so unmounted ones might find themselves taking full damage after a while. If mounting is not a option, be sure to put it on Neutral from time to time so it will inflate by itself as part of the attack behavior.
So bc most comments are from pve players here a pvp tip use them for soaking have them mate boosted veggie cakes yuty roar a deadon on passive healing and a good saddle no heavie or auto will stay in your way with a good gasbag and a food stat deadon