So after a bit of testing, some results. The sample size isnt huge but can certainly get some idea. I would like to know better how to determine margin or error, so if someone could clue me on on that....
Target: Ladybugs (THF), that are either DC or EM and read High evasion when checked. The equipment for melee and tested spells remained the same.
Melee: 1102/2187 (50.39%)
Sudden Lunge: 204/308 (66.23%) +31 acc (expected for most blue spells)
Benethic Typhoon 85/174 (48.85%) -3 acc (likely 0 acc and doesnt recieve +acc that other spells get)
Vanity Dive 160/172 (93.02%) +85acc (I was suprised by this, initally I assumed all spells simply got the +30 bonus but never dropped my melee % low enough on previous tests to determine this. It might actually be more than this.
Heavy Strike: 49/243 (20.16%) -60 (So.....thats 90 acc off a typical blue spell and 145 acc or more from vanity dive. Since I hit the absolute lowest % possible on acc, IT COULD BE WORSE!!!)