Balance issue: Concentration spells are ALL nerfed to oblivion because of the abundance of surfaces. I'm not going to use Bless or Blur when a Fire surface arrow or bomb from a random goblin will make me roll for concentration three times. The only good option is to have less surfaces. Making concentration checks easier would overpower the same spells in other situations.
Underpowered: Color Spray, Acid Arrow, Healing spells (remove the pigs heads and other food items that heal entirely please)
Opinion: The VFX for long lasting protection spells such as Mage Armor, Barkskin and Arcane Ward are far too obtrusive. I hate it when you can no longer see the character properly after just one spell that lasts a long time. At higher levels you will have more effects stacked and it will be only harder to read with multiple heavy effects overlapping. I'm sure most of those could be toned down significantly and/or disabled outside combat. I understand the need for visual feedback but it should be proportional to the actual power level of the spell, and effects can also be visualized by icons rather than covering the character model itself.
