What is best form of attack against wisps ? I also pitched my flame atronach into the fight but she doesn't want to know. Unusual because she fought well against wisp like creatures when ***spoiler** was overrun by similar creatures

Wisp mothers float around like Dragon priests do. The best tactic is to corner them in some place from which they cannot evade attack and hit them with the highest DPS weapon at your disposal or destruction spells till they drop. Ignore the wisps and the shades. Since the attacks of the wisp mother are venom based, poison immunity or a high resistance can turn a difficult fight into a stroll in the park.

They resist shock but frost attacks seem to obliterate them o.0 (I fought against a wispmother yesterday useing ice spike after thunder bolt failed)

I just run up on them and pound them with a hammer. The main thing is to ignore the wisps and the shades and do it quickly.

I had the easiest time with my archer character. Stand far enough away that you can side step her shotgun ice-spike attack. Getting an arrow into her and then dodging her own attack takes some timing, but it sure beats svcking up a ton of damage while closing to melee range.

If you have the time, using fire storm spell/scroll almost kills them. Just a few more sword sweeps and you're done.