looked at the guide. It looks like Incantrix is incompatible with most of the stuff in there though. A lot of it focuses on being an abjurer and taking lost of master specialist or I7V or just being a cleric. So I think I could still make a decent counterer, but not a great one.
Well, the master specialist is for the Minor Esoterica at 4th (which gives you a competence bonus on dispel checks equal to half your CL) and the abjuration CL boost at 6th. And I7V is the grandaddy of all abjuration PrCs. HOWEVER, since you want to do more than just maximize your dispelling, you should definitely go with Incantatrix because it's basically wizard++.
Depending on how else you want to approach things, you could go either:
~~Dispel-focused build~~
Abjurer (not focused) 3/MS 4/Incant 10/MS +2/Archmage 1 (or with early entry, Abj 2/MS 4/Incant 10/MS +2/Archmage 2)
With the planar touchstone feat for +4, and the early entry method for an extra spell power, your dispel check would be: 10 (arcane mastery) + 10 (levels) + 4 (inquisition) + 11 (minor esoterica) = 35, which should be enough for most spells and you would be able to boost that with some buff spells (that you could persist). At level 6 w/ early entry you would have 10 (arcane mastery) + 6 (levels) + 4 (inquisition) + 3 (minor esoterica) = 23, enough to counter or dispel 12th-level casters, which is double your own ECL. Even without the Planar Touchstone feat you could still auto-succeed with Dispel Magic on anything cast by CL 8 or lower.
~~Diviner-focused builds (to know what to do in any situation)~~
Illumian Binder 1/Diviner 1/Anima Mage 3/Incantatrix 10/AM +5
Dream Dwarf Diviner 3/MS 2/Incant 10/Earth Dreamer 5
~~I7V build~~
Abj 2/MS 3/Incant 8/I7V 7
I'm not the expert on debuffs... you could do a fear build, or an enchanter... but I really like the abjurer/incantatrix who dispels/counters, metamagic effect --> sculpt spell or seize concentration or snatch spell to basically take over everything they're trying to do. That sounds really irritating for enemy spellcasters. And, you can persist our own buffs with cooperative metamagic.