I love the concept of this map but where I think it struggles is the chance that it will enter a stalemate condition.
If the players are trying to keep things even between them the board can get into a position where A can attack B but not C, B can attack C but not A, and C can attack A but not B. With the low card trade-in value the tendency is to defend because there's no incentive to earn cards.
Fix the stalemate (increased cards or a capital scheme like 3-Legged Race employs) and the rating goes to 9 or 10.
This is an excellent 2-player strategy board. It's very balanced. I've only played version 6 but some of the other versions look interesting as well. Versions with the randomized starting squares make for some unique and challenging puzzles, making you re-adjust your strategy for each game.