Interesting idea, though it might skew things. Troops like Pharos-Ra can already nearly 1 shot most troops when at full souls, but then again he’s a base Mythic and scales more on souls than magic.
How would it deal with troops that just deal damage, compared to those that do more? Examples:
Muketeer:
6 Red
Deals [Magic+2] Damage to an enemy.
Pride Hunter:
8 Red
Deals [Magic+2] damage to an enemy, and silence them.
Would these scale the same? Would it be left to mana cost to balance out the difference?
For argument’s sake, lets assume the player has 22 Magic (12 base + 5 Magic Kingdoms at 5* (10 Magic) + 2 Guild bonus). Both troops do 24 damage. The Musketeer does 4 points of damage per mana, while the Pride Hunter does 3 points per mana and silences.
If we have a 150% Magic Ratio on single targets (150% of 22), then we’re looking at 35 damage per cast. Musketeer now does 5.83r points of damage per mana, while Pride Hunter does 4.375. Musketeer has had an increase of 1.833r points of damage per mana, while Pride Hunter only had 1.375.
Another example:
Sabertooth Lion:
8 Blue/Green
Deals [Magic + 3] damage to an enemy. Gain 5 Magic if the enemy dies.
Owlbear:
10 Green/Brown
Deal [Magic + 3] damage to an enemy. Reduce the enemy’s Attack by 2.
Assuming the same 22 Magic, both troops do 25 damage. Sabertooth does 3.125 damage per mana, while Owlbear does 2.5. If we increase the Magic by 150% we get Sabertooth doing 36 damage, or 4.5 damage per mana, and Owlbear doing 3.6 damage per mana. Increases of 1.375 and 1.1 respectively.
Also Sabertooth gives us another case to examine, magic increases. If Sabertooth kills an enemy their magic increases by 5, meaning it will do 30 damage next cast, which gives a ratio of 3.75, or an increase of 0.652. Under the 150% rule Sabertooth gains 7.5 mana if it kills, meaning it would do 32.5 damage next cast, which would give a ratio of 4.0625, or an increase of 0.9375.
In short: (aka TL;DR) It wouldn’t be as simple as just giving single target spells a 150% buff, as you’d have to look at a number of other things including mana costs. Not saying this idea is bad, just pointing out that it would favour the lower cost single target spells.