Is level 64-66 good for facing Diantha?

Question

So I'm playing Y and I'm at the Pokemon League. I wanna know if this is a good level for dealing with the Elite 4 and Diantha:

My team:
Greninja-Level 65
Diggersby-Level 64
Lucario-Level 64
Charizard-Level 64
Sylveon-Level 66
Frost Form Rotom-Level 64

Is this a good level for taking on the League, or should I grind more? If yes for the latter, where should I go and what level should I reach?

Comments

Btw, I checked the Type Coverage of your team. Via STAB alone, you cover everything BUT Water/Ground-types. Excellent.

Answer 1

The level range for the Elite 4 are 63-65, while Diantha's is 64-68. I'd probably suggest gaining atleast 4 more levels throughout your team.

But, other than that, you should be prepared.

As for where to grind, I'd suggest grinding in Victory Road.

Comments

Why would you need more levels when the Kalos Elite 4 (and Champion) is the easiest of any generation?

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Because "But, other than that, you should be prepared".

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You'd gain a couple levels by defeating the Elite 4 members' Pokémon too. I don't think leveling up any further is that necessary.