That's not true at all; Tempest is now an inferior source of an identical buff for all other primary melee classes who have their own source (paladins have zeal, fighters have capstone, monks have ultimate wind, etc). every single melee class gains more dps from its level 18-20 enhancements than it does from taking 6 levels for tempest.
There is no reason to have mobility be a completely wasted feat slot; and i don't even have a character with a ranger level.
Tempest used to be excessively good; it is now very overrated as a splash. Exploiter builds used to lead the ac battle; they're now inferior to many plate users.
No one will lose any sleep if tempest rangers incidently gain 2 ac in situations that aren't that important, and ddo gets a feat other people have to consider taking instead of making jokes about. Everyone wins.