if "Bob" marks the bear but does 8 HP of damage, and Tom the striker mauls the bear for 40 hp of damage, does the bear blindly obey the mark and attack Bob, or does self preservation kick in and the bear attacks Tom.
This is a very good point. I am working hard to stop my own group from running through every possible tactical combination each turn. They will occasionally run the numbers too, which I am generally quick to stamp on.Of course, it's also worth mentioning that this sort of roleplaying should be happening on both sides of the table. If your players are all planning tactics like chessmasters and with no regard for the in-game story ("Don't worry about saving the princess yet. She has 50hp and the buzzsaw only does 1d10+6 per round"), you should feel free to act accordingly.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.