Ok GB increase health worked.  I now have over 200 million silver.  I have 6 more fights but since I have so much silver dont need to exploit anymore.  Here is how to do it.

You open client xml and find Dracula, now you want the one associated with Gropu Boss 30, ony my client.xml it starts on line 1920593, go to that line, look a few line above you will see
<healthRating>?</healthRating>, change the rating for each SO30 Dracula line you find.  If you change all <healthRating>?</healthRating> it will change it for every enemy, plus heroes, and you dont need to do that, and I didnt do it that way so not sure what it will do.  Change his health to <healthRating>8000</healthRating>.  Now if you have a favorite hero you like to use do search for them, and change their attack rating.  I know exactly where CAPs and Mags are since I use them in 12.2 or 12.5 for ISO farming.  Once you find the hero you want to use like my example Captain America you will see 100+ hits, what you are looking for his  <cogName>Captain America</cogName>,  now a few line above that you will see accuracy rating which I changed to 100 to make sure I hit, and change attack rating to <attackRating>500000</attackRating>, also you want to change <initiative>0</initiative> to <initiative>100</initiative>, to make sure he goes first in combat.   Now do the same for the other hero, except make that heroes <initiative>80</initiative>, so they will go second in combat.

MAKE SURE to change the health rating for each SO30 Dracula there should 20 of them. 1 for each level variance, and class type.

Now as far as your own GB I havent found the right 5% damage yet.  

You want to use cogName for the hero which is line 14520.  Silver boost as you call it, is a Boost to SO30 Dracula's health so you can get more silver from him as you take him down. 

If you want to use for farming ISO I have CAP and Mags set to much lower attack rating so it takes both of them to take out each wave, so I can get all 20 drops.   I use 20 attack rating for CAP and 80 for Mags.  Since Cap with 100 initative will go first, and mags with 80 goes second.  Also since Mags attack is 80 I can team him with any hero and Mags will take out each wave himself if I need to get xp for the other hero.  There is also some other things you need to change.  1 Caps shield throw on line  209943, look down a few lines and you will see energy.  I changed it to  <energy>0.0</energy>, so that way his shield throw doesnt use stamina.  Now Mags, need to change his gravitation, there is more than one but you only need to change one the other if for the enemy version.  Line 180867 now look down a few line and change 2 things first cooldown from 2 to 0 so that way he can use it every round, and energy 0.  Now I know you can change any attack to an area attack but, when you hit the enemy with a single attak that you changed to an area attack you will only get 1 drop, but when you hit them with area attack you will get drop from all 3 enemies.

https://kh-userimages-us.s3.amazonaws.com/m4QCgFx7199x563ab7564feeb

my silver heheheh
 

https://kh-userimages-us.s3.amazonaws.com/m4QCgFx7199x563ab7564feeb

my silver heheheh