Does this work?

[Corlon]

Is this really obvious and I hadn't noticed it before, or is this completely wrong?

A warlock 4/monk 1 could become an enlightened fist. With that couldn't he channel a hideous blow with arcane fist?

Or does this not work because eldritch blast isn't a "spell" but an "invocation."

Another question related is does the "+1 level of spellcasting class" apply to warlocks at all? If so, does it give more eldritch blast damage and ability to have more powerful invocations learned, or does it just give more invocations known?

 

[Corsair]

Is this really obvious and I hadn't noticed it before, or is this completely wrong?

A warlock 4/monk 1 could become an enlightened fist. With that couldn't he channel a hideous blow with arcane fist?

Or does this not work because eldritch blast isn't a "spell" but an "invocation."

Another question related is does the "+1 level of spellcasting class" apply to warlocks at all? If so, does it give more eldritch blast damage and ability to have more powerful invocations learned, or does it just give more invocations known?

Complete Arcane addresses this, as does Rich Baker's "semi-official warlock errata" thread on the Wizards forums. Warlocks can qualify for any prc which requires a specific spell if they have one with the same effect. (ie- the "charm" invocation qualifies them for Mindbender) They can also qualify for any PrC which requires a caster level only. They cannot qualify for PrCs which require "level X spells", which is unfortunate, because before complete Arcane, nearly every spellcasting prc was written this way (much to the angst of sorcerers everywhere).

+1 spellcasting PrCs do in fact increase warlock invocations known, as well as what level invocations can be accessed, as well as increase Eldritch Blast damage.

 

[Corlon]

Just no damage reduction or fast heal, correct? As those would fall under "other abilities"

 

[UltimaGabe]

Just no damage reduction or fast heal, correct? As those would fall under "other abilities"

That's correct. Otherwise, there'd be no reason to stay a Warlock, would there?

Anyway, back to your other questions, what exactly would be the point of channeling a Hideous Blow through an Arcane Fist? I don't have my book handy so I can't look up the description of the Arcane Fist ability, but all that Hideous Blow does is channel your Eldritch Blast through a melee attack- so since that's what the ability does, what would be the point of applying that through an Arcane Fist, rather than just using Hideous Blow as it's presented?

And, just for the record, allow me to state the (hopefully well-known) fact that Hideous Blow takes a STANDARD ACTION, not an Attack Action- so you can't use it in conjunction with a Full Attack, Flurry of Blows, or Spring Attack.