I think that there are three issues with WebCrypto that people often conflate. But they need to be looked at separately when judging the security of any particular things.

1. Limited algorithms. This is what has use using GCM instead of a stream cipher for our transport layer. 2. It allows developers to shoot themselves in the foot by not enforcing best practices. 3. It encourages crypto delivered over the web.

If (3) is your concern, then it doesn't matter how good, modern, up to date, the methods are. This objection applies to tweet-nacl just as well.

If (1) is your concern, keep in mind that there is nothing wrong with the algorithms and modes we are using. Sure we had to forego some slicker alternatives, but this is a performance hit.

If (2) is your concern then what is true about WebCrypto is true of almost every crypto library out there. Whether we use libcrypto, CommonCrypto, MS CAPI, etc, we have just as great a chance of "using it wrong" as we do with WebCrypto. WebCrypto isn't worse than most of the alternatives, it is just new enough that we all hoped it would be better than the alternatives in this regard.

So given these three general concerns with WebCrypto, you need to make a judgement about how these play out when evaluating 1Password for Teams.