desperation on who?

+spd Tharja's 37 speed with Fury puts her at 40, which outspeeds all 35 and below characters, which is slightly better than Kagero's 38 speed outspeeding all 33 spd and below characters.

The difference is specifically to hit Ike, who sits at 34 spd with Fury, his most commonly inherited A skill set as of this time. Because Ike often carries Quick Riposte, anyone who engages better kill since neither Tharja nor Kagero can tank two hits, and Kagero does not one-shot Ike and so both need to double.

Based on your team composition, however, it appears Kagero might fit in better as a replacement for Klein, although in the current atmosphere, Klein has much better one shot potential. Reinhardt feels like a pain in the butt for your team, so if you have a Nino, I'd recommend a desperation build on her rather than Tharja or Kagero.