Good against hordes, but even better against high-cost, high-save enemy units. Like terminators. The more points-per-model, the harder they are to kill, the better your vindicator performs.
Also fantastic against enemies that have to get closer, i.e., Khorne, Nids, Orks ... set it up a couple of inches beyond their charge range, behind cover, then drive out and shoot after they move closer.
Remember, even if the Vindi doesn't kill 130-150 points of models, it isn't supposed to be efficient. You take a Vindi for the shock value. A lascannon firing over six turns might kill four or five models, but it cannot kill 5-10 models, all at once, right before the enemy assaults your lines. Vindicators can do that.
My favorite Vindicator moments all involve deep-striking enemy terminators or incoming enemy bikes. When you know the enemy will come to you, Vindicators perform best.
Sabre