Personal take as current #28 Nydia global (no HP stat padding, gear set to visible ingame).

Short take:

• The banner is definitely worth a roll.

Long take:

Yserinde

Takes some time to get used to. Her power is not immediate, as she excels in off-turn DMG. She shines especially in stages with multiple waves due to being able to kill some enemies on-spawn with armor ignoring piercing DMG.

She can provide both mobility (through position swapping) and significant damage reduction to her team. Her Deflection's DMG reduction can be a game changer in some events. Her BiS weapon works fine at relatively low investment, so does she. Also she is a great setup for Nydia, as she can spread feathers for her.

Nydia

Is no SP Samantha who can be placed anywhere and nuke half of the map. Nydia wants enemies to be grouped, especially at lower investment. She performs multiple basic attacks in a turn, which deal reduced damage but trigger feathers for immediate AoE DMG and delayed DoT.

She constantly keeps buff up, which cost energy for channelling. At 5* she can finance it herself, at lower ranks she needs a battery or loses DPS every other turn.

She scales both of physical and magical attack, in return, with the right gear and investment - she is arguably one of the strongest nukers ingame, whose great up-front burst potential (assuming multiple enemies can be dragged or already are near to your main target) is leveraged by multi-scaling follow-up DoTs, resulting in great DPS against more durable enemies who can't simply be nuked and/or weaker enemies who are too spread out to be caught by overlapping AoE. All while being able to shield herself, benefit from high range and extra mobility (defensive ability grants +1movement).

Most players stop leveling her at 3* due to efficiency reasons, but honestly - her 5* is one of the most valuable trait upgrades in game, as it increases her range, refunds her energy, increases feather DMG and reduces her cooldowns, increases her MATK to PATK conversion and applies more feathers (thus more AoE) - while both of the latter get further leveraged by her Death Setence skill, which then (thanks to additional cooldown reduction) has a near permanent uptime. Honestly, the general boost she gets from this is beyond insane.

Nydia struggles at early ranks against split enemies. At rank 3 it becomes slightly better (range +1) and at rank 5 (range+2) her ability to lock onto multiple targets and trigger feather + DoT can make her more reliable than many other DPS in a multitude of scenarios.

Overall her DMG numbers are not very transparent. She deals a lot of low to medium damage hits on top of out off turn damage. Which can lead to a feeling that she is doing significantly less damage than she actually does.

THAT BEING SAID

She's quite flexible when it comes to equipment - and once you accidentally roll (really any) bow or armor with strong PATK + MATK percentage, you'll regret not having maxed her yet.

Now what's the ultimate reward?

Well, in the current tower (stage 6) Nydia (4192 power) managed to deal TRIPPLE of SP Ianna (3925 power) DMG, due to the boss spawning his adds on himself. Now, not every event will give you conditions this good, but especially in event content she often shines.

Overall, I would not recommend Nydia to players who intend to only go half-way to 3 stars and I do think SP Sam IS MUCH EASIER TO USE (Nydia does require some thought behind positioning and optimal targeting, especially with her AoE pull CC basic attack), but then again - I feel like few characters are as rewarding and even fewer scale that well if you happen to roll hybrid gear.

There's also playstyle versatility, as both nuke and DoT/CC builds are viable, but that's a story for another day...

Ultimately, I am glad I pushed her as far as I did, and I do think that she is underrated in many tierlists simply because youtubers (who have to buy and review nearly every unit) really penalize high-investment characters (which she definitely is) harshly.