We could probably add x3 speed, although I think I'd rather give the player something more interesting to do with a deck like that because it's kind of a boring and tedious (but effective) strategy. Our next big push is going to be into minion management, where we'll probably be adding ways to upgrade, sell, and maybe even break down or combine units.
The cooldown/delay update nerfs vamp a bit (although jack less so), but I think they're still the best minions in the game. I'd like to keep it potentially just as broken but make it a little trickier to accomplish, so it's not guaranteed best strategy every run.
Thanks for playing and for your feedback!