(3.5e) Some balance questions on a little project

[Shpadoinkle]

Okay, so I'm working on an invocation using class that I'm going to use for a couple NPCs. They are essentially going to be a warlock with the dragonfire adept's breath weapons and breath effects. Eldtrich Blast is going to be limited to dealing either fire, cold, or electricity damage, instead of the untyped damage it deals now, but is otherwise unchanged, and the blast essences (Hellrime Blast for instance) will of course have to be used with the appropriate energy type. I'm shooting for tier 3.

BAB: 1/2 HD
HD: d4
Saves: Will and Fort high, Reflex low
Weapon/Armor Proficiencies: As DFA
Skills: 4+INT/level, probably same class skills as the warlock
Invocations: Learned at the same rate as a warlock, breath effects learned at the same rate as a DFA.

I'm thinking of staggering EB and breath weapon progression, so they're both 1d6 at level 1, but they then alternate advancing every level (i.e. at even levels EB advances +1d6, at odd levels breath weapon advances +1d6) so there aren't any "empty" levels, because I dislike them.

Other Abilities: Deceive Item and Imbue Item as warlock.

The working title for the class is "Black Mage" (as it's pretty much what I'm trying to recreate, with some minor tweaks) but I'm trying to come up with something I like better.

Having Eldtrich Blast might seem redundant and pointless, but the reasons I want the class to have it are 1: Blast Essences, 2: Greater range, and 3: it's not always feasible to scorch an area, say if there are new combatants you don't want to fry entering the fight and therefore haven't had time to apply your Endure Elements invocation to them.

Thoughts/evaluation? I know it's a little lackluster, but it's a class designed to be able to do one thing (BURNINATE!!) pretty well and a few other things adequately.