Nah, Excalibur is powerful but still wouldn't hold up to the Sharlin. If it uses its Main weapon, its dead in the water for a full minute. Plenty of Time for a Sharlin (or its remaining fighters on the off chance the Excalibur actually manages a fatal hit) to dice it to pieces. Lets not forget that other than its Vorlon "I am out of power now please kill me" main weapon, all its other weapons are either Minbari or Earth Alliance, all of which are going to be inferior to the Sharlin's. Its close enough to be a good fight, but as i said, Its most advanced normal tech is Minbari, and isn't going to be their top of the line.