Straight up for survivability Randiuns will trump Warmogs by a long long way. When you have good gap closers like Vi does too and can stick to an AD and use the on-use effect of Randiuns it probably doubles the survivability offered by a Warmogs.
Also pure health will be not great when BotRK is a very very good health shred item now, Id imagine most ADs would happily trade BT for BotRK if you've just stacked HP and have no Randiuns/FH and you'll be gone pretty quickly, Randiuns also doubly scary for them as when they shoot you they lose some movement speed, and thats really quite important to an AD.