You know, that's probably the bitch of the whole thing...in my opinion, two bundles is not an altogether unreasonable investment to finish off an event if we knew up front what we were getting. But the RNG possibility of it only costing one bundle makes it less likely for anyone to take the risk on ANY bundles, because 'fuck you, game.'
Plus, 'fuck you again, game.' I don't want to support a RNG-hell event system. This relative uselessness of this particular tank might make it the perfect one to send the devs a message about their event design.