.
1. Other than via summoned allies, the class seems very low on damage output. Either give it more damage invocations or some inherent means of dealing damage.
2. I'd lose the part of preparing invocations altogether. The class has a finite repertoire and no real means of abusing action economy, so that restriction seems unfair, tedious and annoying.
3. I see no reason why Spell Unbinding shouldn't progress at levels 5, 9, 13 and 17.
4. I'd give the Dabbler means of granting allies resistance vs. dismissal/banishment/wards. It's within reason to choose between this and #1, if both seem too much to you.
5. I notice that Planar Breach is equivalent to a 9th level spell. IIRC, all other invocations are 8th level equivalent tops.
6. Lose the "Width" constraint on the table. It'll make it more pleasant on the eyes. With some more tinkering and formatting, this seems a lot better to me:

Saves Prepared Invocations
Level BAB Fort Ref Will Special Invocations Known Least Lesser Greater Dark
1st +0 +0 +0 +2 Bonus Feat, Conjure Allies, Magical Creation 2 (Least) 1 - - -
2nd +1 +0 +0 +3 Detect Magic 3 1 - - -
3rd +1 +1 +1 +3 Spell Unbinding (1st) 4 2 - - -
4th +2 +1 +1 +4 Allied Augmentation (1 ability) 5 2 - - -
5th +2 +1 +1 +4 Bonus Feat 6 3 - - -
6th +3 +2 +2 +5 Allied Augmentation (2 abilities) 8 (Lesser) 3 1 - -
7th +3 +2 +2 +5 Spell Unbinding (3rd) 9 3 1 - -
8th +4 +2 +2 +6 Allied Augmentation (3 abilities) 10 3 2 - -
9th +4 +3 +3 +6 Bonus Feat 11 3 2 - -
10th +5 +3 +3 +7 Allied Augmentation (4 abilities) 12 3 3 - -
11th +5 +3 +3 +7 Spell Unbinding (5th) 14 (Greater) 3 3 1 -
12th +6 +4 +4 +8 Allied Augmentation (5 abilities) 15 3 3 1 -
13th +6 +4 +4 +8 Bonus Feat 16 3 3 2 -
14th +7 +4 +4 +9 Allied Augmentation (6 abilities) 17 3 3 2 -
15th +7 +5 +5 +9 Spell Unbinding (7th) 18 3 3 3 -
16th +8 +5 +5 +10 Allied Augmentation (7 abilities) 20 (Dark) 3 3 3 1
17th +8 +5 +5 +10 Bonus Feat 21 3 3 3 1
18th +9 +6 +6 +11 Allied Augmentation (8 abilities) 22 3 3 3 2
19th +9 +6 +6 +11 Spell Unbinding (9th) 23 3 3 3 2
20th +10 +6 +6 +12 Dual Conjuring 24 3 3 3 3