Tower Craftsmanship gives 1% better tower effects per skill point, 10 max.
The idea is that all tower effects are slightly stronger. Some towers, e.g. Manitou, won't benefit from this, since their effect can't be better without being much more powerful.
Examples of effects at 10 points in this skill:
Dandelion area effect is 36% damage (was 33%)
Herb Witch's attack speed bonus is 22% (was 20%)
Pickpocket has a 27.5% chance to pick pockets (was 25%)
Ripper gets a 110% attack speed bonus on kill (was 100%)
Ganesha's xp bonus is 22% (was 20%)
Huli can now eat 55 bananas (was 50)
Scarface has a 33% chance to burst (was 30%)
Mr. Iron takes 168 seconds to construct (was 180)
Holgar has a 1.1% chance to find mead (was 1%)
Rabbit gets third carrot at level 14 (or 14.4?) (was level 16)
Electric chair gains an extra chain attack every 12.6 levels (was 14 levels)
Bear Hunter's area effect is 44% (was 40%) -- Could also reduce the air penalty from -70% to -63%. Probably not though.
I don't think any of these effects are overpowered. I think this is quite weak compared to some of the other wizard skills, so I would set a high minimum level so it isn't unknowingly chosen before more useful skills.
My biggest concern is implementation. I don't know how these tower attributes are coded, and this might be a moderate amount of effort on Andy's part.
I forgot to consider the harder to balance towers, the ones that scale and carry. Below are those towers:
Wolf gets 1.1 xp per pack kill (was 1 xp) - pack bonus unchanged.
Muli gets 11% chance to drink (was 10%) - drink bonus unchanged.
Shadow gets 5.5% chance to adapt (was 5%) - Max adapt and adapt per hit unchanged.
Solara gets 44% area damage (was 40%) - Burn damage unchanged*.
Phoenix rebirth takes 9 sec (was 10 sec) - Or I guess damage increase could change to 15.4?
* Increasing burn damage would increase single target damage as well as area damage. Increasing splash leaves the single target unchanged.
I think that the basic idea is great. The problem is that it gets kinda inconsistent how/which skills are affected so you would need a big explanation (see what you wrote) to understand this. Which is Tedious...
I'd imagine it just happened without any more explanation than my first line about increasing tower effects.
Maybe Andy could dynamically update the cards to show the adjusted stats once in game for transparency.
Or, maybe it could say "increases each towers' first effect by 1%" Then any cards with two effects could put the effect to be scaled first.
A similar idea would be to increase the current scaling effect towers get by 1 level per point.
E.g. Ganesha gives 20% + 0.5% * (current level) bonus xp. In this version of the skill, 10 points would give it 20% + 0.5% * (current level + 10) bonus xp. That would basically give it 5% extra xp bonus to the area.
I think the idea is decent as long as the effect is:
* Clear and easy to understand.
* Easy to implement by Andy.
* Not overpowered.