I've been thinking:
Mark of the Wyld: I'd like to see the bonus of each attribute be proportional to the target's attributes. The total bonus (37*5=185) would remain unchanged. Ex:
Original Attributes Bonus Attributes Final Attributes
str 4str 20str 24
agi 5agi 25agi 30
sta 8sta 40sta 48
int 10int 50int 60
spi 10int 50int 60
total 37total 185total 222
Ex: warrior
Original Attributes Bonus Attributes Final Attributes
str 200str 50str 250
agi 160agi 40agi 200
sta 200sta 50sta 250
int 80int 20int 100
spi 100int 25int 125
total 740total 185total 925
Analysis: the buff might work the same way as Blessing of Kings. However the attribute part of the bonus would be better then BoK when the sum of all attributes result in a value less then 1850 (185/10%).
PS: I know my english is horrible. Please, talk about the idea, not about my grammar.
edit: added the warrior table.