Originally Posted by
Cernunan
Warlock is a bad fit for most melee builds, as it's "melee" tree isn't optimized for melee, it's more viable as a tank build. Sadly warlock doesn't multi class very well at all since your dps is determined by your warlock level. There are some pure warlock tank dps aura builds that work at end game, but they really are about as boring as a build can be (you tank up and defend while enemies sloooowly die in your aura.)
Honestly what you are picturing would probably be eldritch knight Wizard/sorc, at least the EK is optimized for melee. AS a different alternative maybe the alchemist Vile chemist works, but is a bit more optimized with simple weapons then martial, so it's a little more difficult to work into a monk build