Doctor Proctor
First Post
As a side note regarding Defender's Gambit, the major downside is that it costs the victim something. There are cases where a monster would choose not to lose his one immediate action to make a basic attack. If the monster has, say, an immediate action teleport power to get out of Dodge, then he won't react to this daily and that really sucks for the fighter. Instead of an immediate action, this should be a free action on the part of the victim.
Again though, that's one of those corner cases that's unlikely to happen most of the time. Pulling up the Compendium I did a search for level 15 standard monsters with the keyword "immediate", and got 39 results. Sounds like a lot though, right? Well, there are 116 creatures total at that level though, so that means that maybe a third actually have powers that use immediate actions.
Even still, many of those that do are limited to things like once per encounter, or when they're first bloodied. Meaning, they might easily not have access to these immediate action powers when the Fighter uses this power on them, and so they lose nothing.
Point is, you can come up with 101 corner cases where these cirmcumstances might be more or less likely. However, if you just pick a random monster, fast forward to a random round in the fight, and the Fighter uses this power, with all things being equal why would they ever attack the Fighter? What benefit is there to ever do it unless you're sure beyond a shadow of a doubt that you will drop the Fighter with that attack (in which case, that was a poor choice of timing on the Fighter's part)?