Drain spells doesn't have the +5yd forgiveness range

[Lelol]

What is the bug?
Drain spells doesn't have the +5yd forgiveness range

What kind of bug is it? (Quest, Class, Spell, PvE)
Spell

How can you reproduce it?
Duel someone, cast drain life on him, have him slowly move out of the max range of the drain life spell, drain life will stop instantly.

Please describe, in detail, what is suppose to occur when this bug happens:
The spell should continue to drain until the target is (spell range + 6yd) away from you.

Please describe, in detail, what happens when it bugs up, and how it's malfunctioning:
Stops instantly upon max range.

Evidence providing proof of bug:
http://webmup.com/EJQ71/

Download it, go frame by frame, look at the drain life icon at the bottom, when it turns red it means he is out of range, the spell keeps going for what looks to be about an additional 5 yards or so. Look at the combat log right after he is out of range, it gave him health from drain life, so it's not just visual.

Didn't look much for footage but I'm sure I could find more.