What combination of tanks should I use?

Yesterday I pulled an Edvard and a Brogar

My current team:

Rhee tier 5 (S)
Erondragas tier 3
yomoco tier 4 (S)

on the side:

brogar
edvard
estine

So I was testing king brogar out, and when he is blocking, I don't see the DEF reduction for some reason, so he might be a viable tank

Edvard has pretty high HP and DEF, almost as good as Eron, can poke at those squishy mages in the backrow, problem is he has low DEF for a tank, but makes it up in HP

im only lvl 47 right now so I can actually have a chance to snap a dragas mine from the treasure pit
so now, my team works well, and I plan to replace yomoco with slayers harry once I get him

2 tanks and 3 back row is the most optimal setup I'm pretty sure. I would probably use brogar and erondragas for now and transfer when you get a better tank like allon or something.

His damage is really bad... putting him in the front would just make him die faster than if he didn't block for other tanks, and putting him in the back leaves the frontline vulnerable. Edvard has decent HP and DEF, and also has some decent damage output, like eron or hanzen. So why brogar and not edvard?

I've never used Brogar before so I wouldn't know too much about this, but I feel like Edvard and Erondragas would be too frail of a frontline since both of them are somewhat offensive warriors.

I always keep a tank warrior on the top and an offensive warrior on the bottom. That's just my preferences.

I got a rogas today. He is quite a bit better than my current 2, without the DEF cut and self heal and all.

I also rolled a merila, and 2 awakened ygress

Ygress is kinda bad later on, but she is awakened, so ill probably level and tier until I get something to transfer.

My current team: (player lvl 52)

Rogas (tier 2 [cant get mats right now])
merila (tier 4)
rhee (tier 5 (S))
erondragas (tier 3)