Changes in the most recent patch 10.23 are buffing the champions mid-lane viablility.
You mostly saw her on the rift as a support, soon you might see Seraphine much more frequently in the mid-lane. As developer Mark Yetter disclosed, the development team is currently looking at adjustments to Passive, Q and E ability that would favour her in higher level and scaling situation over the support role, at the same time nerfing lower level damage to bring her baseline damage output as a support inline.
Yetter attached the following potential patch notes:
We are pushing the distinction between mid and support Seraphine. Mid Sera, who will be higher level through the game, will have better access to scaling damage via the Passive and Q changes and can now use E more comfortably for waveclear when needed. Support Sera won't be able to hit those same levels or damage numbers, but will still be able to lean on E-max to provide consistent CC for her team.
BASE MANA REGEN: 10>>>8
Passive - Stage Presence
NOTE RATIO: 7.5% AP >>> 6/7/8/9% AP (level 1/6/11/16)
Q - High Note
DAMAGE: 55/65/75/85/95 (+55% AP) >>> 55/70/85/100/115 (+40/45/50/55/60% AP)
E - Beat Drop
BASE DAMAGE: 60/85/110/135/160 >>> 60/80/100/120/140
DAMAGE TO MINIONS: 60/70/80/90/100% >>> 100%
Support is quite good right now, so these shouldn't remove the position, just bring it to a reasonable state.
Currently, Seraphine is sitting at below par winrate on most tracking services suggesting that she likely isn't overpowered despite her relatively high pick rate in the support position. Time will tell if Seraphine will require additional adjustments and if Riot will react to them further.
Image via Riot Games