I don't know how the Grand Mastery Patch works with ToB concerning attacks etc, but this is how it works if you have D/L'd it for use with BG2. It apparently corrects the attacks etc to conform with D&D rules. Effectively it makes the BG2 rules work the same way as they did in BG1. I'm not sure at what levels fighters etc gain "natural" benefits to speed etc. But this may help some.
points spent.......to hit bonus.........damage bonus......attacks
1 (Proficient)...............0...................... ....0......................1
2 (Specialized)...........+1........................ +2....................3/2
3 (Master)................+2........................ .+2....................3/2
4 (High Master)**......+2.........................+3...... ..............3/2
5 (Grand Master).......+2.........................+4....... .............3/2
** Improves weapon speed.
This gives you an extra +1 damage at High Master. Although if you installed TeamBG's weapon specialization "fix" it will restore this chart to what it was in BG:
points spent.......to hit bonus.........damage bonus......attacks
1 (Proficient)...............0...................... ....0......................1
2 (Specialized)...........+1........................ +2....................3/2
3 (Master)................+3........................ .+3....................3/2
4 (High Master).........+3.........................+4..... ...............3/2
5 (Grand Master).......+3.........................+5....... ................2
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It's bleedin dark down here, slippery too.

Man, that's a pisser.