Developer Ghostcrawler has posted the following information regarding the new deterrence:
We built this ability primarily as an Arena tool. It isn't going to help you much in a one-on-one situation. It will buy you time to get a heal or to have an ally deal with the player attacking you. You can also buy a few seconds of life in order to Disengage or the like.
The directional component is something we are trying. It may not fly and we're prepared to change it if it doesn't work out. We wanted the hunter to have to do something other than just pop immunity and run away, but we also realize we ask an awful lot of hunters in general so this just may be too much.
We are much less likely to remove the inability to attack. We've had trouble with defensive abilities being used offensively and don't want to get into situations where the hunter lols at the melee who is up on top of him while he (the hunter) merrily takes shots at the healer.
One of the biggest reasons we wanted to change the spell in this way, though I understand it may not mean much to some of you, was to get a great visual in there of the hunter just parrying stuff right and left. It can look cool and it can be a visible indicator of what the hunter is doing rather than asking people to pay even more attention to tiny buff icons. It is hard to overestimate how much good art can help an ability feel cool.
Now long term, something we are going to explore a lot more is just plain juicing up hunter melee capabilities. You've got mail and you've even got some melee weapon strikes. If those were actually scary abilities, then a melee (or caster) class that closes with you risks taking a beating. The hunter could choose to flee or stand and fight. We're not talking about giving hunters a viable melee option (like Survival has flirted with a couple of times). But imagine your melee damage was 80% of your ranged damage. Ranged would always be preferable, but melee would be a decent last resort rather than pretty pathetic (as it is now). I want to stress that this is a long-term change, not something you'll see in the next patch or two, and I'll be the first to suggest that it may not work out. But it is an idea we're discussing.