You have full e2ee between yourself and Mullvad but crucially Mullvad don't know who your IP. Five eyes are already doing SIGINT on behalf of both the US and the UK government before my connection even reaches Obscura so I lose nothing but potentially gain privacy.
How is it you think a single company (Mullvad) having access to my IP and what I am browsing is less secure than splitting it up amongst multiple providers one of which being Mullvad with that audited platform you talk about?
If I wanted Tor on top I'd layer it on top too but that would still be a single point of failure.