DFG does 15% of max health and then amps all inc dmg by 20%. Thus, if you are playing eve, and you use your DFG first, than you will so 15% + 0.85* (15/20/25)% *1.2. You can just put 0.85 and 1.2 together, so it's actually a 1.02 modifier.

This means with the new nerf, eve will do 15% + (15.3/20.4/25.5)% max health damage if you use DFG before you ult.

On the other hand, if you use your ult first, you will lose the 1.02 modifier, which means you will just do plain 15%+(15/20/25)% dmg. So it's still a good idea to cast dfg first.

No big change there. But what's really important is the range nerf. 

Before, you could cast your ult out of sight range, and manage to hit someone. This meant that you could initiate with suprise... but at the cost of that extra dfg dmg. Now that the range on the ult has been nerfed, DFG has become better on eve by comparison, simply because there is no more reason to cast ult first.

Of course, this is only based on damage. There are still many reasons to cast ult, such as a aoe slow, for shield. But damage wise, you should always cast dfg first now.