that it would.
in ancase when dealing with a multclass deal whether or not if its one or more base classes or with one or more prcs, what you have to look at is what does
warlock gain to loose in the mc deal, with enlightend mind you loose pretteymuch all of your invocation choices, while gaining being immune to fear and be able to look menacing to your opponents, you gain a select few invocation with this build, but you can fly with it.
the eldritch disciple, what you stand to loose
3 lcls of warlock, 3 lost invocations
what you stand to gain: being able to heal yourself
turn undead, more invocations, more invocations
gift of divine boss( takeable multiple times)
the eldritch thuerge
what you stand to loose: weak familiar, one arcane spell lvl, EB damage,
what you gain +1 to arcane caster lvl at lvl 2 up, more invocations at lvl 1 up
wacky comobo
warmage 5.warlock 5. ET 10
with battlecaster you can use both the invocations and arcane spells in medium armor
a 2o warlock looses nothing and gains nothing , but can use just about anything.
since your evil tiefling warlock is rancidly rotton, im going to share with you some knowledge of feats:
fiendish heritage feats will aid a tiefling and basically turn it into a half-fiend with those feats, and there is about 4 of them and along with the fey heritage feats they will stack with the abilities granted by the warlock and the tiefling