Yeah I was gonna say something along the lines of what he said. Especially the fact that the bond pair has a mind link which lets them communicate also despite being trapped she's not deaf to our world. However for communicating it's pretty simple he can talk for two or she can just you know user her chalkboard and any nearby reflective surface to answer stuff. Or more dramatically like use the fire magic for some sort of golem or avatar. 

And for teamwork usages outside what was mentioned is she can be like a glorified HUD/ mission control given my dude's armor is shiny meaning she can be literally be another set of eyes and ears.

Also I like the pairing it gives a nice little heroic pathos and plot hook. Since there's a knight in shining armor and a damsel in need of rescuing.