Some kind of family bonus maybe should also be given to heroes of the same class as they know their fighting style and powers between them eg. when fighting with 3 druids in the team (alby,vela,noor) a 10% health bonus can be energised 0r when having 3 barbarians in the team you can get a 5% attack bonus on them. That way is also fair by the fact that emblems are divided to many heroes. Same can be done for a full paladin team which can have a 10% defense bonus as they are fighting like a roman turtle with all shields around them! What do u think, should SG devs provide Class Synergy Bonus ?
Actually not a bad idea,as long as everyone is emblemed don’t think it would cause that much chaos. plus it’s not like it will be used that much if you in a raid your not gonna pic a class over a element
I like the idea a lot @Harry21. I think there is some merit to it. 
I think there are some minor tweaks I would suggest for consideration:
1- Rather than how family bonuses work where you get an increase per member, I would suggest a range for the class bonus:
“If you have 3 or more Rogues then “blank” happens regardless of if you have 3, 4, or 5.
The thought being while for most players this is a nice and balanced perk, the big guns out there with every 5* maxed, etc can likely exploit this and make some crazy stacking bonuses with families, classes, and specials.
In your example of +10% attack if that stacked with a family attack bonus you’re looking at say a Grimm +20 with +20% attack, which is insane. It brings people with those roster to a whole new tier. Limiting the bonus as I described can hopefully keep that in check while still giving a manageable boost to us “norms” 
2- Rather than make up new abilities, I would vote to increase existing ones. Keeping with rogues for example:
If you have 3 or more rogues on the same team each maxed rogue gets an additional 5% chance to dodge or something.
The thought being:
A - You don’t want unmaxed and unemblemed heroes to gain that ability. IMO opinion that would be OP.
B- A flat increase for where a hero is at is important to avoid it being OP too. If I have Jackal with enough emblems to have a 10% chance to dodge, this brings it to 15%. Where as my 20% chance Scarlett goes up to 25%. Saying everyone would go to 25% to account for maxed heroes getting a benefit makes it OP too IMO.
Super cool idea though. The more I think about it the more I like it, kudos!
Thanks buddy, hope many more cool ideas (like the ones you shot) surf up a bit more before too long!