Too much power loss... It's better to divide the griffons with a +2 bonus to all stats, so that berserkers can be used effectively against them...
Why griffons? The answer is simple, because they are large...
And even better would be paladins with a +1 bonus to all stats; they are already immune to berserkers... But then the question arises, where can you find so many units?
I don't understand the idea; can you explain it in more detail?