I just had a Fortress Defense match that the Orks won by holding A, which almost never happens. And the ENTIRE match, I was a stormboy with a power klaw, jumping the wall and punching tanks, or taking out rhinos once the gate was down. Punching the siege tank was especially effective, as hitting in at the right angle would spin it, making it miss the gate. I even had one moment where I was thanked by an Ork in a quadgun near A, as I punched the siege tank JUST as it shot, making it go wide and miss the turret. Obviously, other races just send out a team of meltas to destroy tanks, I've faced that a few times as well. But, with proper cover fire, we still got a shot at blunting those attacks before they even get in the walls. I'm not suggesting everyone do it, but maybe next time you want to go tank punching with me. At the very least, you will keep the enemy busy when they all turn around and shoot you to save their transport.

I get where you're going with this, but really, you're relying on the enemy to be stupid, and that doesn't make a solid strategy. Against a coordinated team, you're not going to make much headway. Even if you kill a rhino, they'll just spawn a new one immediately, and you likely just wasted a ticket.

So I would only ever use this against siege vehicles, where you would get a much greater benefit. Just hang out on the walls protecting lootas, then dive on the siege tanks. That is the only time you will outperform the lootas for AV (before the walls go down).

So, yeah, viable strategy, but you just have to apply it properly.