This is an area where my DMing philosophy is under active development. I read a blog last week that was going through the various defender class pros and cons, and that article LOVED the Battlemind's punishment mechanic and thought it was borderline overpowered. I, on, the other hand, have been running a game where the defender is a Battlemind, and she's NEVER gotten to use her Mind Spike in three levels of play. This is because she can only Mind Spike an adjacent enemy, and if a marked enemy is adjacent to her, it attacks her.
However, I ran the first session of the Dark Legacy of Evard season of D&D Encounters
last night, and on several occasions I had the monsters shift while adjacent to the Knight (getting punished) and in one case attack a different PC than the adjacent knight (getting punished - although in this case, the monster succeeded in killing the other PC). I know it was a lot more fun for the Knight to be able to use his punishment mechanics - and the battle was plenty hard even without me playing the monsters "optimally".
In the case of the Battlemind, I think part of the problem is that it's a 4 PC party, which means that it's rare for the Battlemind AND another PC to be adjacent to the same monster (they don't seem to flank much), so the monster either attacks the adjacent Battlemind or MOVES AWAY to attack someone else (provoking an opportunity attack, but not a Mind Spike).
I definitely will look for more opportunities to let my defenders punish monsters for ignoring marks when it makes sense for the monster to do so. More fun for everyone!
Is this an area that WotC has written much about? I don't recall a lengthy discussion of this topic in the DMG, but I think it deserves one.