I am thinking of starting a fight with a CC spell like Overwhelming Wave from stealth with the Assassin bonuses for increased damage, and longer CC from a crit from stealth.

It will work well IF Overwhelming Wave does all hit rolls in one go (like a Fireball or a Blizzard would).

I never tried it with Overwhelming Wave but I suspect it works a bit like Rolling Flame, where the enemies in the line get hit one after the other. If that is the case then the first hit roll will lift stealth/invisibility and remove the assassination bonus. So you would only get it for the first enemy - which would be a waste.

Maybe try it out with the console before committing to such a character. I would do it but am currently on a family holiday without access to the game.

If it doesn't work with Overwhelming Wave it can still be worthwhile to use assassinate with other spells which hit all enemies at the same time. Like all circular and cone-shaped ones basically (Touch of Rot, Blizzard, Hail Storm, Embrace of the Earth Talon and so on) and of course the single target ones (Sunlance is devastating with assassinate for example).

If you are set on using Overwhelming Wave (is is a cool spell) and it doesn't work with assassinate, you could switch to a Hekwalker and get much more damage and longer CC time out of Overwhelming Wave that way. A Helwalker can get up to +12 accuracy (Enduring Dance of Death), +10 INT (Duality of Mortal Presence and +15 Might (Thunderous Blows + Helwalker passive) as well as +2 PEN (Thunderous Blows). The increased INT also grows the AoE sizes alongside the longer durations, something an Assassin cannot do. And those bonuses are not limited to stealth or invisibility.

The added MIG (up to +15) and INT(up to +10) work especially well with all pulsing spells and DoT spells because both will add more damage (one directly and additively via dmg per pulse/tick and the other multiplicatively by adding more pulses/ticks via longer duration).

Another plus of the Helwalker is the Swift Strikes abilities which lets you cast a lot faster (+DEX and an action speed bonus). You can pair that with a Cat Druid's Cat Flurry, resulting in fantastic casting speed.

Long Strides helps to get out of danger mich faster. But you can also do that nicely with Assassin's Escape and either Smoked Veil or Shadowing Beyond of course.

Assassinate has the advange of the whopping +25 stackable accuracy - which is ofc. pretty awesome to have.

Edited 1 hour ago1 hr by Boeroer