End Game Strategy
Never, never, never underestimate the power of the teleport scroll. The strategy we used is for everyone to carry a scroll, go to an area where there are quests, or a boss and wait for the dead king to get within 1 movement turn of you. Then teleport to the other side of the map preferable to a shrine to restock your teleports. Move, fight, let him catch up teleport away and do it all again.
That way you can avoid the Dead King forever and Level up unlimited times so that you can have every stat have at 100 or above.
This game really needs an endgame trigger. There is no chance to actually lose the fight against the dead king.
Do not get me wrong, I love the heroes, the synergy effects and the leveling up, but the missing endgane trigger needs to get fixed.
1.) Disable the teleportation scroll at a certain time (after six cities in total got destroyed).
2.) Trigger endboss battle after six cities in total got destroyed.
3.) Integrate Level caps for Power up cards so that every Power Up card Uses up a gear Slot as well.
The Valley of the Dead King was meant to be more of a sand box experience, presenting players with a great many options. In all the games we've played, we haven't seen ranks above 30. Of course, the time spent powering up is largely up to the players playing.
Some like this and some do not. You can certainly house-rule any of these options you've presented above. Personally, I would not integrate the Power Up / Gear upgrade take the same slot. You'd lose much of the thrill of leveling your hero that way.
Alternatively, we would suggest you add Shrines to the Dead King's list of targets, and then the Black Market once those fall. When he takes all 4 shrines, and then the Black Market, he'll be moving at 12 hexes per turn. Most games however don't last this long, as players become confident in their ability to face him.
Thanks for the comments and suggestions however.