In the notes for 1 Tim. 3:11 the Reformation Study Bible says the following.
their wives. Lit. “women” This verse abruptly interrupts the section on deacons. Its meaning is contested. The “women” are probably either the wives of the deacons or themselves deacons. The abruptness of the insertion probably reflects Paul’s concern that women, in particular, have not fared well at the hands of false teachers (2:14; 5:15).
Seeing how the topic is “deacons” it would be very strange to change the topic abruptly, and then change back to the topic of deacons in the next few verses. I would also find it a little strange if the verse is talking about women deacons, mainly because the verse before and after talk about men. Therefore, I would say that “women” in this case are the wives of the deacons themselves.
I have heard some who believe that 1 Tim.3:11 refers to “women deacons” quote from Romans 16:1 saying that Phoebe was a deacon. However, the Greek word in which we get the word “deacon” can also be translated “servant”. Versions such as NIV, NLT use “deacon”. While other versions such as KJV, NKJV, ASV, NASB (footnotes “deaconess”), use “servant”.
Thinking about the context of Romans 16:1, I don’t see any clear indication from the context that the office of “deacon” is meant here. In fact, when I think of the qualities that Paul says that Phoebe has; I see qualities that all Christians should try to emulate.
Looking at what William Henriksen and Simon J. Kistemaker in their New Testament Commentary says concerning this matter. He seems to be saying that the “women” are “deacon assistants”, who have the same qualities “dignified, no slanderers, temperate, reliable in all matters.
Tom