RIT

Possibly. However odds are he'd rather have his Shardspear in most situations where he would use the reverse lashing. And the constant contact would me he'd have to be physically touching syl throughout to make it work I think.

I think the power differences come more from the "More than the sum of their parts" concept. Yes both Jasnah and Shallan can Soulcast, And Shallan can also make standard illusions. But what makes Shallan truly a Lightweaver is her ability to use those illusions to transform people. From what she does to the deserters, to what she does to Sedarial. She wraps herself into an illusion that shapes how people view her and themselves. I agree with Truthwatchers being 5 because while in the end Renarin might be able to use illusions and progression separately what makes him a Truthwatcher is the ability to use them both to see what comes next.