I shot a mule deer (204yds.) and an elk (128 yds.) with tape on the barrel. Those were in CO with open sights. You have a big hole that can allow a lot of moisture in over the course of an extended hunt, especially if you don't change your load each day (and I don't).
I switched from using balloons to electrical tape because tape stays on much better. The only issue that I have had is that after I shot the elk, I was reloading and a piece of tape was still over the muzzle that deflected a bit of the powder. The bull was still in sight, but moved off before I could replace the primer. I found that bull dead, and after getting it packed out I just shot off the load before I tried to fill my deer tag. It would have only taken a second to pull the remaining tape off, and I won't have that issue again.
The Thor bullet worked as advertised on the elk. Ditto on the deer.
I too use the electrical tape with good success. In my case, the tape did not blow off the barrel, I just shot through it. This year I hit heart from 120 yards so I do not feel the accuracy was comprised in anyway. I had to learn the hard way as to why folks put tape or barrel condoms over there muzzle. I was hunting mule deer in 2009 and it had been a miserable raining day. I never thought water could get into my barrel. Fortunately, I didn't find the buck I was looking for, but on the way back to the four wheeler I happened to see yellow in my barrel. I ended up looking down my barrel (not smart) but saw my sabot only 6" from falling out. I had been carrying the gun upside down as I thought that would keep water from getting in there. Apparently something had gotten in and the sabot was slowly sliding out. Since then I have been using electrical tape and have killed 3 bulls from 170, 80, and 120 yards respectively.