I found our doula helped DH to help me not took his place.
When I had low back ache she showed DH how to do counter pressure on my back to take the pain away so he could be the one to do that for me not her.
When it came to transition and I scuttled off to the cloakroom bellowing 'I'm going to have diarrhea' she didn't follow me, DH went after me. She was there when the MW was ordering me off the toilet as DD2 was about to be born, reminding me that it would soon be over and baby would be here I just had to listen to the MW.
I had the doula on one side and DH on the other while I delivered DD2, both encouraging me but she never took over she just echoed DH's encouragement (as in DH - 'You are doing so well TS', Doula 'Yes, you are doing really well').
She also reminded me when the 1st MW (not the one who was with me when I had DD2) checked me earlier in the labour that I didn't want a exam while contracting and why but she didn't tell the MW to stop. I can't remember the actual words but it was something like 'TS, you wrote in your birth plan you didn't want to have an exam during a contraction because you wanted to focus on the contractions and have less pain' so I was able to say to the MW, 'Can you wait till this is over?'.
All in all she was fabulous, she melted away once baby was born, she supported DH to support me, she reminded me of what I wanted when I was too focused on birthing to remember and she all round made DD2's birth so fabulous that DH asked if we could have a 3rd baby before I had delivered the placenta (nearly getting a slap from the MW for that in the process though
). Which was a far cry from DD1's birth when DH was seriously considering booking in for a vasectomy immediately so I could never go through that particular experience again.
I had the doula for DD3's birth and the only reason I am not having her for DC4's birth is that she has retired from doula'ing.
Your DH's experience of the birth would be enhanced if you have a good birth experience, and statistically you are more likely to have a positive birth experience with a doula than without. And even if it ends as a crash c-section at least you have the doula to be there with you while you wait for the theatre and to be there for your DH while you have your c-section. They are worth their weight in gold frankly. They are you, your DH's and your baby's advocate.