Hardest gym to take down?

Do we get to use the "big 19" in the battle?

It has to be Gym3 out of your choices.
Everything else is just going to be blown up by 2-3 Dragonites, zero thought, and minimal dodging of charge moves only.

If I want to make a Gym Hard in the Sense of Damage it would be like this
1) Blissey 3kish ZH/DG
2) Clefary 2kish ZH/DG
3) Snorlax 3k ZH/BS
4) Dragonite 3k+ DT/DC
5) Lapras 2.2k Ice Shard/Hydro or maybe WG/IB (I want 1 water 1 ice to hit both dragonite and tyrantir)
6) Eggy 2.5k Conf/Seed Bomb

Now if I wanted to make the Gym hard in the sense of time consuming to hold with Golden Rasp
I'd drop either #5 or #6, move other to 6th. Put in Chansey in the other spot.

Now if I wanted to make this a Gym that lasted 8 hours and was at a long intersection.
I'd move Chansey to 1st to lower decay and make sure a car at light didn't take it out in 1 go. Keep Clefary 2nd. Put Blissey/Snorlax 3&5 Dragonite 4 and 6th spot

When making a Gym I consider the 5 Best Attackers:
Dragonite, Tyrantir, Machamp, Mew2, and Raikou
Goal being not to let any of those attackers dominate 2 pokemon in a row.

Why does it matter? All gyms are easily taken down. However, if I had to vote I would go for #3 being the "hardest" because it's the only one with both a Blissey and a Chancey.

(Swiftly thought and subject to further reasoning)
From hardest to easiest:

3,2,1,5,4