4th Gen Are my pokemon good enough for the Elite 4 on Pokemon Diamond

Here are some pokemon that I might use

Dialga, Lvl 47: Metal Claw, Ancient Power, Dragon Claw, Roar Of Time

Abombasnow, Lvl 40: Wood Hammer, Mist, Ice Shard, Giga Drain

Empoleon, Lvl 44: Metal Claw, Rock Climb, Waterfall, Surf

Garchomp, Lvl 50: Earthquake, Dragon Claw, Sandstorm, Crunch

Luxray, Lvl 49: Thunder Fang, Spark, Charge, Crunch

Staraptor, Lvl 50: Aerial Ace, Double Team, Close Combat, Fly

Lucario, Lvl 50: Quick Attack, Swords Dance, Aura Sphere, Bone Rush

Weavile, Lvl 36: Faint Attack, Night Slash, Agility, Icy Wind

Are these pokemon good enought to challenge the Elite 4

I'd recommend using one of your two ice types personally, with Abomasnow being the better of the two choices IMO just do to certain members of her team being vulnerable to grass types in diamond.

I don't mean this in a completely bad way, but you are heavily underleveled. I'd get your team to the high 50s or possibly low 60s. I'd recommended picking whoever you plan to use and begin to level them up.

I'm posting this with no idea if you know the story or not, and if you don't, I don't want to ruin it.

I honestly would go with Staraptor, Garchomp, Empoleon, Abomasnow, Dialga(if you can switch metal claw with flash cannon), and Luxray.

This team covers every type plus most of them are pretty fast and can pack a punch. Just be careful when going in. I looked up the movesets for Cynthia's team and she really has some competitive movesets.