Blink has had problems since release ; ) Though it's more of a problem because of buggy terrain or a change in terrain rather than the spell itself.

The brain freeze change makes sense (instant free fireballs procced off ice lance would be kinda cheap).

I just hit 70 right before the 3.0.2 patch, and have been enjoying the Ice Lance/insta-Fireball punch greatly.

I'll miss it, but it's not a gamebreaker for me.

I hate the fact I can't blink through a lamp-post, a fence, a barrel, or something I can jump over or move 5 inches to the right and go around.

Be reasonable, Blizzard! I'm not trying to Blink through a wall or an impenetrable barrier!

And don't get me started on hills.

I thought it was just me and lag that was causing blink weirdness. About 50% of my blinks don't work.

Blink fails on "flat" terrain for the same reason you can't blink off a cliff, the spell stops you at the edge of a terain piece. The positive is this keeps you from appearing in mid-air if you use the spell near a real cliff.

The downside is that areas like the infamous tunnel in WSG, while appearing flat, are actually built as two different pieces of the world (the tunnel entrance, and midfield). When you try to blink into the tunnel, the blink spell thinks you are attempting to blink off a "cliff," and stops you at the invisible edge. Combined with lag, this gives the appearance of blinking nowhere or backwards.

I highly doubt the problem will ever be fixed at this point, as they'd have to rework the world architecture and/or pathing models of the entire game. Best bet is jump before blinking (this helps prevent getting stuck on the small rocks), and experience will tell you when to wait a additional second or two before casting the spell.