So are you referring to a 1v1, Or do you have team mates that could help peel? You mentioned putting blood horror up while you setup gate, that is just asking to get reflected. You should have your team help stop the charge (most classes can do this)
Blood Horror can not be zerker raged out of either, if you don't keep blood horror up on cool down for them to reflect then you should be able to get it off and when you do it should be full duration unless they are on Mortal Coil or Psychic Horror DR.
As a warrior it's basically a guessing game as to when a good warlock is going to pop blood horror. You have to pre-reflect before he casts the spell. Think of it in the same sense as fear ward, if a priest runs around with fear ward up you are most likely going to wait until it gets dispelled. However if the priest casts fear ward as he sees another priest running in to fear then it was a skilled usage of the ability. Same can be said for blood horror. It's all about timing.
As far as spell reflect only working for instant cast spells... that's just silly. Granted if you've been playing a Warrior for a long time it is rather common to reflect deep freeze, Mortal Coil, Death Grip, ect. That would make the skill completly useless for new to moderate players. Imagine if you could only "lock out" instant cast spells with your pet...
With all that being said, warriors have always been a counter to warlocks. But currently there is no real counter to warriors and they do need some tuning. Blizzard has already addressed that they are "looking into it" which will most likely mean they will over compensate and make warriors dissapear again (has happened for the last few seasons warriors have been viable).