Did you ever get around to fixing the Ninja Perk?

Ninja multiplies your critical chance by 1.15 instead of adding a flat 15%. This makes the critical chance bonus worthless. [Taken from the Wiki]

Er, multiplying something by 1.15 is the same as adding 15%.

Depending on how the perk is suppose to work. It reads "+15% critical chance with Melee or Unarmed attacks. Sneak attack criticals do 25% more damage." So, assuming you have 50% change of a crit, adding 15% to that equals a 65% chance. However...

50*1.15=57.5

The wording can be off and/or misleading. I would assume, by reading it, that it directly adds the 15% to your over all formula ie base+weapon bonus+perk bonus not cumulative (for a lack of a better word at the moment) ie (base+weapon bonus)*1.15.

edit: Though, it really becomes a moot point if you can get your crit chance to be 87% before taking this perk.

The language of the second part of the perk works the right way how you suggested. Hope this all makes sense.