Were there Valar who didn't have Maiar helping them?
 

I believe there are quite some few for wich don't have the names of any Maiar serving them:

as far as i know we got:

Manwë:Eonwë,Olórin
Ulmo:Uinen,Ossë
Aulë:Sauron,Curumo
Varda:Olórin,Ilmarë
Vana:Arien,Melian
Estë-Melian
Yavanna:Aiwendil
Oromë:Tilion,Allatar,Pallando
Melkor:Balrogs,later on Sauron & Curumo,Ungoliant?,Thuringwethil?,Draugluin?

Wich all in all means that we don't have any Maiar serving Tulkas,Námo,Nessa,Irmo or Nienna.I suspect these would nevertheless have Maiar serving them or could there be such thing as a Vala without any Maiar in their service?

There are hundreds, probably thousands of Maiar. Just because Tolkien does not name every single one does not mean they did not exist. Anyways Olorin is a deciple of Nienna, not Manwe

The Maiar/Valar relationship seems to have been far more fluid than is usually recognized.

Some Maiar, most notably Gandalf but also Melian, serve or have served more than one Vala. Melian is named as a follower of both Vana and Este. Olorin is said to have served Lorien, (judging by his name he was originally associated with dreams or visions) but became a disciple of Nienna, (Lorien's sister). According to 'The Istari' in UT he was then chosen by Manwe and Varda as their emissary to Middle Earth.

What this suggests to me is a Maia could 'diversify' his/her interests serving and learning from more than one of the Valar either simultaneously or serially. And that career change was a definite possiblity [img]smilies/wink.gif[/img] .

Not a great track record ... [img]smilies/wink.gif[/img]

defintely not a good track record........but we shouldn't forget Aulë might have hundreds of other Maia serving him who would have behaved better...or not.

It seems that the ValarTulkas, Mandos, Nessa, Lorien or Nienna do have maiar but they are simply not mentioned in the histories of men. Those which have been mentioned by Noxomanus , but I found another maia, in the Simarillion that you did not include. I think he/she is a maia of Ulmo-

Salmar A maia who entered Arda with Ulmo; maker of Ulmo's great horns, the Ulumeri

yup,i forgot that one

Regardless of which Maiar serve which Valar, ALL Maiar serve Manwe really, as the High King of Arda. I think somewhere it says Olorin "travelled" to the houses of Nienna and Lorien to learn from them...so maybe he is a disciple of Manwe but learnt from other Valar also. Who knows [img]smilies/smile.gif[/img]