Additionally, even though the M-5 proved itself to be an effective battle controller in engaging the Lexington, Excalibur, Potemkin and Hood, we have to remember that Enterprise's phasers only scored a handful of hits against Wesley's task force. Given how well Kirk's Enterprise weathered more substantial attacks, I always found it hard to accept that two or three well-placed direct hits would be all it would take to both wreck a starship and kill an entire crew, particularly if Wesley's ships (presumably) had their shields up.
Seemed that the Excalibur folded a little too easily, don't ya think?