Additional Notes#

Dusk's Notes#

In theory, T91 is as good of a night AR as 9A-91 and AS VAL, with all of the minor differences going in her favor.

At base, all 3 of T91, 9A-91 and AS VAL fire at the same frames, and while 9A-91 and AS VAL has a FP buff of 180% over T91's 120%, T91 has the additional 10% crit rate (20% -> 30%) as well as the 9 or 12 base FP over the other two, and this is enough to cover the difference between them. Additionally, T91's skill last an additional 2 seconds, which is the point that pushes her over 9A-91 (if 9A-91 does not have her unique equipment).

However, there are multiple issues here, ranging from very specific to ultra specific.  

• Not significantly better performance-wise than 9A-91: In terms of pure damage, T91 and 9A-91 are equal for the first 12 seconds, and many battles do not last that long. If the battle does last that long, T91 DOES have the extra edge for 2 seconds. However, this is only true if 9A-91 does not have her unique equipment, as when she does, T91 never catches up to 9A-91. 
• Crit damage is calculated after armor: This diminishes the edge T91 has over 9A-91 agaisnt most armored enemies. Note that this does not make T91 weaker than 9A-91, but rather closes the differences such that T91 never actually gets a solid lead over 9A even if you increase the enemy's armor. That said, at any point which 9A-91 actually does better than T91, neither of the ARs actually do any good. Still a small ultra specific issue. 
• Harder-to-use Tiles: While T91's tiles opens up strong [b] formations, she does not work well in a [F] formation (as OTs-14 benefits more in the 7 position in a [F] formation). A [b] formation has the weakness which your position 7 DPS might be attacked directly by enemies when your concentration lapses (as you have to move your MT around to block enemies every fight). For that matter, T65 also doesn't do well in a F formation, or any 2 AR formation for that matter. 
• Much more expensive core-wise: T91 costs 43 more cores to use than 9A-91, which is significant for many players that are still choosing units to build.
• T65 exists: T65 is a 3* monthly login unit that, for whatever reason, has better stats than T91. While her final output is lower than T91 due to her weaker skill, T65 is a significantly cheaper (core-wise) option if you do have her. If you missed getting her, she may pop up in a few events, and probably eventually stay permanently in an event campaign map.
• Unlikely to get a Neural Upgrade: 9A-91 has a better chance of getting a Neural upgrade as she is a 4* unit, and AS VAL has one already. Even when 5*s will get Neural Upgrades, there are other, weaker units in line that are more likely to get Neural upgrades. Admittedly, T91 is at the weaker end of the older 5*s, so it is not impossible for her to get a Neural upgrade. 
• (Future) AS VAL MOD2 exists: Theoretically, with fairies, having a mix of crit damage and damage is better than going pure damage. With better crit rate than most ARs, it can be argued to use T91 with AR-15 with crit damage fairies for a higher overall DPS. At least until AS VAL MOD2 appeared and removed any chance of T91 standing beside AR-15. That being said, this is something in the future, so T91 can still have her spot beside AR-15. 

In the end, her largest issue is not being significantly better than 9A-91 (and T65 exists). It is up to you to decide whether you want to get 5 cores or use 43 more cores for a marginally stronger 9A-91 instead of duping/training 9A (or 84 more cores for a marginally stronger T65 instead of durping/training T65). Regardless, she is definitely 'usable' despite the multiple issues raised, if you end up deciding to train her anyways.

With a Crit Fairy with maxed skill and Crit 2 talent and UMP45 + Five-Seven, you can get 100% crit rate during her skill. Just in case you want to live out that fantasy.