Strategy within Heroscape is an ever-changing beast and I absolutely love that fact.
If you have been holding out hope for a Heroscape Strategy bible, don't hold your breath. Strategies that may absolutely apply in one situation within a game might be the worst thing you can do later in the same game. You
honestly cannot cover every situation that is going to come up within a game. Being that Army composition can vary greatly (and hopefully is constantly changing with new releases) and that the "board" never has to look the same from game to game, it would be impossible to develop an all-encompassing strategy guideline. With each "Wave" release and each new map design, yesterday's specific counters may become obsolete. There will never be a defined "opening move" for Heroscape.
However, that being said, there are still plenty of high-level strategies...