Yes, You are missing the Global Bonus from Arena.

Arena gives you 2 different things:

1st - Medals to upgrade your Great Hall bonus

2nd - Global Bonus which is given based on your Arena Tier Standing.

You would have to get to Platinum Arena.

Here is a picture for example:

i

I am in Gold 4.

I am getting the 20% Global Bonus for being in Gold 4.

You can see what I am saying from the Green Highlighted Squares.

Platinum Players are getting the 25% Global Bonus for being in Platinum.

These bonuses are applied to your heroes stats.

They benefit everything you do in the game.

Here is a picture for example: 

i

@Kalindra   ......Thx for asking.   I was curious if that bonus was arena only or all battles.  

I've noticed "Clan" column on the screenshot. Is it new? Is it for some future clan activities?

I believe great hall bonus is for champions that belong to a particular faction, the arena bonus is for all champions, the bonus itself is all all battles.  

The great hall bonus is't related to faction.  It's for all champions of the right affinity (magic, force, spirit, void).

you are right, i meant affinity, not faction, so great hall bonus for void is meant for all champions of a certain affinity

Maybe it will be for Doom Tower?  

I believe the "Clan" column has always been in the game.

Most people over look it or don't pay close attention to it.

I think the game originally put the column in for future clan related stuff.

I think the game is planning to have Clan Wars in Raid.

They just haven't implimented any Clan Related stuff at the moment.