Make Blizzard IV instant. Here's why:

[Malevicton]

I don't think you're examples are very good. If you hit Benediction or Hallowed Ground it goes off. It might be too late, but it registers. Using B4 3 seconds out, then having to interrupt, will require another ~3 seconds. So now its plan further ahead just in case. Interrupt twice and now you need more than 6 seconds, and so on. Also, no BLM was not always played this way. In 2.X, AFIII falls off you put it back up with a single cast. Enochian falls off and you're using you're 2.0 rotation for 30 seconds...

Oh c'mon, your argument against the examples is semantic. As for planning ahead based on 3 interrupted casts... if your cast is interrupted 3 times then you didn't plan ahead.

[Sensyon]

Oh c'mon, your argument against the examples is semantic. As for planning ahead based on 3 interrupted casts... if your cast is interrupted 3 times then you didn't plan ahead.

Well, not really. Its not the same at all, but you tried to say it was to help your point. There's a difference between not timing you're instant action abilities perfectly versus timing your cast abilities perfectly and having to interrupt them. The former is you're fault completely (outside of server lag issues) and the latter can be manipulated by outside forces (mechanics, AoEs, etc.) If you can see the difference, than half of your argument is moot. As for the second comment, I agree to a point. However, what do you do if you don't have SC, and you interrupt your cast to avoid an AoE, but by the time you can be stationary you don't have enough time to cast B4? Bismark EX, for example. You interrupt your cast or wait to cast it, because a puddle forms, and now its following you..?