I like Delilah and Verity, I'm not crazy abotu Hosanna. 3 so unusual names together are a bit of a mouthful IMHO. Personally I would get rid of Hosanna. DelilahVerity has a great flow.
Gorgeous! However I like two mn's but this does seem a bit too long...maybe you need a shorter name for the second mn? How about Osanne or Ozanne which are the french forms of Hosanna?
Strangely, it flows well though each name is 3 syllables. It seems a bit...long however? How about DelilahVerity or DelilahHosanna? Or I prefer Hosanna to Verity, but the DelilahVerity flows better, so I don't know which to choose. XD