I'm well aware of the characteristics of the La-7. I've been here 2 and a half years and I flew the La-7 for a a few months after it was released. Thanks for the heads-up.

But, the spit 9 gets more kills and the P-51 is far more prevalent than either (going on last tour's stats). I think the La-7 has a worse k/d too. Frankly the spit and P-51 are all over the sky, yet all we hear are whines about the La-7.
It certainly doesn't unbalance the arena.
The La-7's low speed handling characteristics are poor - worse than either of its VVS stablemates. Worse than the spit and P-51. It has a vicious stall.
Frankly complaining about the La-7 in relation to the mossie is a bit redundant. A well-flown P-51, Yak or Dora should be able to dominate any fight with the Mosquito.
Basically if you let the La-7 get you into its optimum combat regime, you're dead. But you can say that about the spit, zero or nik.
Always choose the contrary regime, whatever aircraft you are fighting.