Griffon is pretty much just a DPS race. Just make sure you time your buffs and debuffs so you don't use them before he strips/steals them. Brogni is great for this, as is any CA champ.

+1. 

On top of timing buffs/debuffs it's a big time DPS check to see whether you're geared properly. 

If you get a chance maybe post roster and what you're using and see if anyone can help. 

 Well I put my top 4 dps champions + Vrask in the team and manualled it as best I could and very nearly killed the Griffin. I think that for the moment I just can't pump out enough damage but I should be finally getting tier 6 masteries on my core champions tonight so that should be enough to get this done.

 My best runs used Roric for the speed aura and I have to say he did really well with his stun on the waves and Scale Breaker on the Griffin. He's a lvl 50 right and dies too easily but I think he's got some real potential. Elhain and Vrask did well too because they don't buff or debuff anything so they could care less about the Griffin's abilities.

Do you mind posting your roster? I'm curious to see what you're working with. 

 I'm in the middle of a big string of autobattles to get those masteries but my notable champions who are actually built for use are;

6*

-Elhain

-Geomancer

-Vrask

-Frozen Banshee

-Coffin Smasher

-High Katun

-War Maiden

5*

-Ninja

-Roric

-Kaiden

-Reliquary Tender

-Valerie

-Gravechill Killer

-Shieldguard

-Armiger

-Zephyr Sniper

 I've got a number of other really great champions like Occult Brawler, Demytha, Madame Serris, Dhukk, etc that will definitely get built but it's a matter of food, gear and books. Once the masteries for my clan boss team are done there'll be more energy for that but at the moment moving up to nightmare level is my main focus.

I'm not sure if you're using Ninja in your clan boss team, but he would be a really nice DPS option for you, against Griffin.

You don't want to many champs with debuffs on their A1. You can't control when the debuffs land, and the Griffin does not only transfer debuffs to you, he also gets a 5% turnmeter boost for each debuff transfered, and as far as I observed, that is per champ. So if one debuff on the Griffin is active, he will transfer that to all 5 of your teammembers and gets a 25% tm boost from that. Debuffs on cooldown skills are no problem, as you can time them, so the debuff expires right before the Griffin does his transfer attack.

And you definetly don't want turnmeter manipulation in this fight, neither your nor the Griffin's turnmeter.

Ninja would be an exeption, even with decrease def and turnmeter boost on the A1, because his damage is so insane. But he should have 6*, not only for this fight, in general.

The Griffin does an extra hit to champs that fall below 50% hp, you need some healers that bring up the hp of all champs close above 50%. Do you have Apothecary? He is fantatsic in this fight. Don't use the turnmeter boost, just the healing skill and the A1. 

Vrask is a sure pic in this fight. No debuffs and the healing from his A1.

 I'm using Geomancer for clan boss rather than Ninja but I would like to 6* Ninja for generalized content. I seriously underestimated how much energy it would take to get WM/GS on all my clan boss team, I'm getting close but so far only Geomancer has gotten his tier 6 skill. I do expect to be able to kill the Griffin once I get there, if I can get War Master on Vrask I think I'll have it.

 100 days in and no Apothecary despite pulling about a hundred ancient shards and thousands of mystery shards. High Katun is a great speed champ but there are times when you don't want her aura and Apo's heal would be nice. Still I can't complain too much, I've had some really great epic pulls.

I'm a filthy small spender and buy monthly gems then just spend them on masteries for what ever champion(s) I'm working on that month.

I can't stand the Mino grind and as you said it takes a lot of energy. I think the best strat is once you six star a champ just go grind to 60 in Mino with them and you will get full masteries+60.

If you're like me and spend a few bucks a month I just pot to 60 and buy the masteries. Probably shit advice tbh but it speeds things up a lot.

  Yeah, my account is kind of out of synch from where it should be because I went for couple fusions when I really wasn't ready and now I'm doing a whole team to tier 6 at once. It's a brutal grind. :-) I've spent about $30 on the game so far just to help support something I enjoy, if I were to spend some more it'd be on the monthly gem pack or a really nice void shard offer. I've saved up thousands of gems I thought I'd convert into shards but I didn't need them, I could end the suffering at any time but I figure I'll finish the Minotaur grind sometime in the next couple days and save the gems to help with a fusion or something.