Both Equpment and unit merging have gotten great boosts! 
short ansere for both
1. Equpment not boost bace stats as well as give a flat rate so even low leveled equpment helps
2. Mergered untis now double in strength every Qality point

Long anser For Units

 1-2 X1 so at 2 (1+1)  you will be twice as perful as you were at one
2-3 X2 but at 3(2+ (2-3 = 2) so 4 total) you will be twice as pwererfull as you were at 2
3-4 X4 (3 = 4x (3-4 = X4) = X8 ) At 4 you will be twice as powerful as you were at 3
to try and make this any more clear lets say your at a quality of 3.15 (becase you are)
qualtiy of 1 = 1
3.15 -1  = 2.15
then 
the next point is worth X1 stats bescas 1 to 2 is worth X1 
1+1 = 2 so at 2 you are twice as powerl as 1
so 2.15-1 = 1.15(now is when things get fun)
2-3 is worth 2x
so total of 2+2
1.15-1 = .15
.15 X4 = .60
so total mutliplyer = 4.6X vs Normal strangth 
with current formula ti would be 3.15
at 4.15 it would be 
4+4 = x8 at Q4
and 
.15 X8 = 1.2 so X9.2 stranght

Equipment

For each level of  equpment the assosiated stat on that equpment get a 1% boost. 
so if you have an equpment that boosts Def and Att at level 20  
and a equpment that boosts Deffece and HP at level 15

you would have a deffec boost to sats (befor taking in equpment bonus) of
Def = 35% 
Att = 20%
Hp=15%

Chests have been reduced in rarity and increased in gem quantity also removed popup for chests.