This is why it is important to develop good working relationships. I get people bouncing ideas off me and I do the same with them. It prevents a lot of friction further down the chain.
There are people across the disciplines who want to be cabinet makers who are forced to live in a flat-pack world. A good working relationship with such people makes one hell of a lot of problems go away.
If your devs use EF and C# then it is worth gaining a working knowledge of EF and C#. In any software development "it depends". If a C# developer is sympathetic to DB concerns and a DBA is sympathetic to C#/EF concerns then that answers one of the "it depends".
A lot of poor practises and behaviours get badged as "Agile" when those are actually the antithesis of what agile development is about. James Shore's Art of Agile was the thing that made me think about Agile in a positive light. Before then my exposure to it gave me an extremely negative impression. The 2nd edition will be out shortly and having read many of the early draft chapters I'm going to buy it even though I have the 1st edition. There's a lot in either edition that made me think about how the disciplines from the Agile world could apply in and benefit the DB world.