Normally, I resolve touching a foe in combat by adding his DB and OB used against the PC trying to touch him plus/minus appropriate mods, roll d100 + appropriate mods (Agx3) and if the mnv roll is higher, touch succeeds. If roll is failed, PC attempting the touch is subject to an attack equal to diference between target number and amount rolled for mnv.
So if foe has a 45 DB, the sorceror will need to roll a 46+ to land his touch of disruption. If foe is attacking sorceror with a +70 OB, then Sorceror needs to roll a 115 to succeed.
Normally I define touch as laying on a finger, a slap, or use of a wand, staff, rod, etc. Wants are +10 to roll, rods are +20 and staves are +30. Rarely have I allowed use of melee weapon (and thus the OB for the weapon) to be used. I have allowed brawling and martial arts ob's to be used, but at a -20 to BAR and MA OB, as if using TWC. The mnv roll or the BAR will suffer an additional -20 for off hand, depending on which hand is declared for what (assuming SCSM is successful, of course, even if spell could normally be auto cast, though auto cast is aqllowed if an OB is not used to mod the mnv roll).
Sounds complicated, but its not.