for my new caster, when it was at level 4, it was a sorc2/monk2 with cha 20.(18 init stats, +1 from enhancement, +1 from leveling) It used the following for Niac:
- eagle splendor, +4 Cha / +2 DC
- conjuration focus item +1 DC
- double conjuration focus, +2 DC
The exactly DC is 10 + 1 (spell level) + 5+2 (cha modifier) + 2 (spell focus) + 1 (item) = 21
I went straight to kobold ring leader right after creation. On normal, it's land by 80-90%, and usually one shot any kobold. On hard, it usually either one-shoot or drop the kobold's HP by 80-90%. On elite, it require 2+ shoots to kill a kobold. I don't remember the percentage for hard/elite and it is for sure lower than normal.
for shocking grasp, I don't use any electric damage boost item/clicke, nor put any action point. My Niac deals with 2-3 times more damage than shocking grasp.
I've just reset my enhancement to max both fire/ice and acid/electric lines, and did a quick test in Tear of Dhakaan on normal. the mobs in the first room and the first bridge should have around 70-80 HP, and with greater potency, my niac hit at around 70 and most of them are killed in one shoot or becomes almost dead. shocking grasp hits at around 40 and it takes 2 hits to kill a mob. In this case, a fireball/acid blast + niac works much better than shocking grasp to me.
the key issue is landing rate. for the Tear of Dhakaan test, other than the two bowmen, the landing rate is 90%. I tested twice on bowman, the first time I missed niac 3 times and success at the fourth shoot; in the 2nd time, I one-shoot killed a bowman in the first shoot. For niac, I seldom use it to shoot at sprider, merphits, rogue, and archors. When I run low level quests in solo, i usually use niac to kill all melees and casters and use my rapier to kill any archors.
I don't know about the other damage spells, but, imho, Niac is definitely better than Shocking Grasp because of its high damage figure and high landing rate.