Well I aggree that elements may not be useful for some setups. E.g. for my current setup (even though that may change). I rather like arcania and that's a must for warlocks definitely. But I'm a conlock anyways
Overall I think warlocks are a very good and versatile class. You can have many different setups, as you like. A few speels need work on IMO, to become really useful.
BTW I thought Corrupt Blood is a damage over time spell but had to see that it isn't. Has this been changed or am I just rembembering it wrongly?