If you only want Ninian, pulling on everything just to raise the pity rate is most definitely not worth the cost in orbs and chances that your pity rate will be broken.
Only summoning blues is the best strategy here by far, even if it means resetting the batch a lot.
Also, I don't think it's ever mathematically preferable, even for people that would appreciate any 5* unit, to ever pull for a non-focus orb. The pity rate increase is not worth the extra orbs spent.