Fane of Slaanesh question

New AoS and Slaanesh player so please be kind as I'm trying to learn and figure the game and the faction out.

I have the Fane of Slaanesh ready for painting and I'm struggling to see any real tactical advantage to using it.

The D3 wounds seems much to steep a cost for very minor choice of benefits that you have to pick only 1 off.

Given how little health most units have, even if I used the ability on sigvald it could potentially take nearly half his life for 1 turn of only +1 benefits to a roll where he may not even get to use it. I can see some benefits to his charge rolls perhaps if certain he will get into combat but even then the benefit seems iffy.

Is there something im not seeing, an angle i dont appreciate here? Any seasoned players that can offer some insight or is this just another area where slaanesh have been short changed and left wanting?

Im literally sat in bed comparing faction terrain benefits with my fiancee who plays stormcast and thinking this really sucks for us.