TL:DR
DK has great sustain, to that end they don't have an escape. However against large groups in PvP the lack of an escape causes positioning errors to really hurt. Add an escape functionality to DK Take Flight?
Recently rolled a HybridDK, and boy. I can see what y'all are talking about in that it has shite mobility if you're a melee char. Snares and whatsit make you a sitting duck, and whereas a NB has Shadow Image/Cloak, a Sorc has Bolt Escape, Warden has Major Expedition/Vines, DK mobility is kinda crap. Sure 2H snare removal is nice, but that is lesser by far.
And, TBH, I can see how against a zerg it just becomes a tidal wave of pressure you can't really escape, even just to get get back to your allies front. Making any positioning error a huge penalty that you can't really recover from unless you're specced tanky.
Now, I still think that the DK tradeoff should be extra tankiness in exchange for a lack of mobility, but they kinda need an escape skill.
To that end, I think by allowing Take Flight to be both an Offensive and Defensive ult might give the DK some unique flavor in their kit.
Here's my thought:
Turn it into a Quick-cast and/or (Uninterruptible) channeled skill.
Quick Cast: pressing the ultimate button will treat it as the normal skill, auto-aiming at your highlighted target. (Or failing if no target)
Held: Holding the ultimate button for at least a second, turns it into an AoE Ground Targeted skill, and the longer you hold it, the longer the range you can fly. up to a maximum distance at 2s Channel (or something).
And when I mean that it will increase the range, I really mean it. Allow you to at least double the jumping distance (Balance sake probably the summed distance than just the horizontal distance), and let the DK really fly. Either into battle (but now the skill is dumb-fired), or retreat to safety.
By sticking it behind the Ultimate, this type of mobility can both be a strong escape/engage tool, and still restrict the overall mobility of the class to compensate for its small-scale sustain.
Of course, it may need to be tweaked based on the terrain around keeps and such (no leaping onto them), and have a failsafe state for when lag mistakenly thinks you held the button rather than only pressed it.
What are your thoughts?