I understand what you mean. But you have to take account that Erza is like a diesel : she always begin a fight at "low level" and then enhances her stats in the fight, sort of a Hulk who increases his stats during all the time's battle. And her stamina-durability are her best weapons. I see her as the best tank in Fairy Tail.
Having huge average against Erza at the first round is classic : see Ikaruga, Kagura, Azuma and all her fights. Defeating her while she is finally serious is clearly a different thing.
Laxus fights with his strength without restriction from the beginning, but his stats doesn't increase.
If I can make analogy between these two, I can say it's Thor vs Hulk in comics. Thor is stronger at the beginning of the fight by some mergin but Hulk increases his stats until equal him and then reverses the situation after a long battle. This is how I see Erza vs Laxus's fight.
So, you can see Erza vs Laxus as bs, but for me, it's classic in fact. It's Erza's way of fighting. Nothing more....
. She always hold back the first half of the battle.
If Erza manages to fight Suzaku in the labyrinth, you will see that she will be useless the first half of the battle until reversing the situation to a draw or a victory if she taps into PoF miracle.
For Grey, Yes he can put a battle for sure. He is smart, durable, strong, fast and a good versatile Magic. I vote a High Diff victory for Laxus because I think, if Grey is really serious he can hurt him before being defeated. For me, the weak link here is Lucy. I like her but can't do anything. Replace Lucy by Wendy and my vote can be different : Berserker Grey with Deus Eques can possibly reach Erza's result vs Laxus.