Just a thought, but why not get rid of this carry-over from PnP?
The +4 dodge bonus while tumbling is generally not worth a full feat in DDO. It was taken before to get Spring Attack (SA). SA was formerly worth the requirement of taking this fairly useless feat because of 2 reasons:
1) Ranger tempest I - was a full on increase in attack speed, also was a +2 AC bonus that would stack with a shield clicky/wand. Now the number of builds out there with 6 levels of ranger has decreased significantly. Six levels of Barb is the new poster child for dps. The limited +10% chance to proc an off-hand attack isn't as powerful as the former speed increase. And the AC is now typed as a shield bonus (non-stacking). So why not remove one of the prerequisite feats (there is no other enhancement line out there that requires 3 feats for it's 1st tier).
2) Spring attack and the abuse of "twitch" fighting - People may argue that SA was worth taking 2 prereq feat as it gave a +4 to hit while moving... and people used to be moving all the time. But with the dearth of movement while attacking these days (due to losing glancing blows and the changes to attack animations) and the insane to-hit bonuses out there... SA is no longer worth spending 2 more feats to get it. Especially since the +1 AC from dodge is only useful for fully twinked high end AC builds.
My recommendation is that Mobility be removed from the game, or at least removed from the sequence (Dodge/Mobility/Spring Attack). That way any folks that really want a +4 AC while tumbling can take it. But most others can skip a fairly weak feat and just have 2 prereqs for their Tempest I or that +4 to hit when attacking those fleeing mobs (**** you fearsome armor!).
Just my $.02... feel free to flame away!