Soulstealer Vayne needs particle effects on her base model, like Hecarim.

Soulstealer Vayne, quite frankly is a massive disappointment. It's a 10 gem skin (150+$ worth of boxes), that is most comparable to a 975RP skin. The issue comes with the fact that she has basically no abilities. Her Q is just a dash and makes her glow slightly, her W is not much more interesting than her default skin's W, her E looks like an auto attack, and her R does basically nothing because it's a steroid.

The only way to fix this with Vayne's current kit is to add particle effects to her base model like Hecarim. Give her base model a particle effect similar to the effect she currently has with Q empowerment. Make her Q empowerment cause her to glow like she's leaking light. Coat her large (ultimate) crossbow with shadowy particles.

The big issue I think most people have is that her base model is just incredibly boring. You expect her to be on par with legendary skins if not better. Particles would be the perfect way to fix this. Basically make her always look like her Q empowered form and make her Q empowered form even more dramatic.

Hecarim's particle effects for reference: https://4.bp.blogspot.com/-LdFbX-wvEdI/VwZtb7VNZAI/AAAAAAAANNc/XatkE8AgdIoTzqRm62tv0unypAYL_dBOQ/s1600/hecarimturn.jpg