How Countermagic Mechanic Works
It is RNG, so not matter how much you pump it, there is a chance for something to get thru. And you could get bad RNG where it does not block anything, or good RNG and it blocks everything.
Playing as Lo Pan, with no access to buffs or anything decent to cast, counter-magic is about the only option. I’ve found it blocks a fair amount even with just overcasting to 20’ish. Plop it down on turn 1 to get the most out of it and pray to the RNG gods.
When fighting against a death mage, it blocked Weakness most of the time, and Life Drain a fair bit. When fighting against Merlin, it blocked a fair number of buffs. I’ve never had it stop Web, not sure if Web cannot be blocked by counter-magic, or if I’ve just had particularly bad luck in that regard.