I rarely rehydrate and my beer comes out awesome everytime. Dry yeast has more than enough cells in it for a 2.5 gallon batch. I'd even be willing to bet that it would technically be over-pitching for that batch size if you use that many healthy cells. If i wasn't lazy, tired and on my phone I'd check mr malty
Edit: remember he already had 1/2 vial of liquid yeast in there as well.