Help me optimize a controller-warlock that doesn't just spam Eldritch Blast

Question

Control wizards have been a fun thing for me to play in many editions of D&D. Looking at the Great Old One Warlock, it seems to have some potential as controller. With Tome, I get the Thorn Whip and Vicious Mockery cantrips, and some nice illusions.

In my previous question, I got good advice on how to make an effective warlock. However, it seems to be very focused on Eldritch Blast spam; I would prefer some more versatility. I would rather have more options and versatility at each point in time to act tactically instead of a single best-optimized thing to spam.

House rules are the same as in the question before: We do get both a feat and ability bonus at level four, at which level the campaign will start. Variant Humans are allowed. We are allowed to raise stats to 16, for a cost of 12 (as in playtest, different from PHB, where 15 is the max). Multiclassing is not allowed.

What options are there to make a great controller Warlock?

My current idea:

• Variant Human Great Old One Warlock of the Tome
• Tome Cantrips: Vicious Mockery, Thorn Whip,
• Invocations: Repelling Blast
• Feats: Moderately armored, maybe Crossbow Expertise or War Caster
• Weapons: Shield

The character has good AC and can go into melee. He can use Vicious Mockery to give disadvantage, or Thorn Whip and Repelling Eldritch Blast to move the enemy around.

War Caster would open up OA, while Crossbow Expertise would allow easy use of ranged spells while threatened.

Good answers either present suggestions on how to improve my basic idea or a different Great Old One controller build. Alternatively, an answer that shows that a controller like in previous editions is suboptimal (either in general or given my preferences) would also be accepted.

Answer 1

I was thinking about this too, so here's my build (added an additional Feat from your houserules):

Lvl 4 Tiefling, Archfey Tome Warlock

This build points to forgive the melee and AC options for a more focused caster. I liked your idea of an hybrid, but seems to me that it really needs to be an hexblade, going in the direction of the other classical builds around. Tiefling adds some interesting features, while allowing to reach 20 CHA on lvl 4, increasing the overall effectiveness and chance to hit of the few spells you can cast.

By Lvl 4 you have:

• Cantrips: Eldritch Blast, Minor Illusion, Vicious Mockery, Thorn Whip, Shocking Grasp, Thaumaturgy, Friends
• Lvl 1 Spells: Hex, Sleep, Faerie Fire
• Lvl 2 Spells: Hold Person, Phantasmal Force
• Hellish Rebuke 1\day (2d10)
• Fire Resistance
• Agonizing and Repelling Blast

I chose Archfey over Old One for several reasons:

• Spells: Dissonant Whispers and Tasha's seems kinda redundant to me, especially when you can get Hold Person at lvl 4. Sleep it's an excellent spell vs. low level mass enemies, it has no concentration and grows with spell slots. Faerie Fire can grant advantage to the entire party vs one or more hard targets. Both pacts have Phantasmal Force which is a great disable for low int enemies and fun to use too.
• Pact Powers: Fey Presence is an area disable which fits more the theme than Telepathy granted by Old One. At lvl6 Entropic ward is fine, but Misty Escape is simply awesome.

Invocations: I'd go to PimpMyBlast just because this is your only reliable source of damage in a lot of situations where CC or forced movement are not options - If all CCs fails, if you want to blast that minion in the backrows not worthy a spell, in long fights, ecc.. But if you like, you can forgo one of the blast invocations to get rituals, which can give you a bit more flexibility and a Familiar.

Feats: i'd really like going first at all costs with this build, so i'll take Alert. A well placed Sleep or Hold person the first round is no joke. Otherwise Moderately Armored can give you better ac with a shield, but going melee will require War Caster too to be a viable option.

Ability scores in order of importance: Max Cha, High Dex, High Con, Mid Wis, Low Int, Low Str

Role: cc\secondary caster

Playstyle: Disable high treat enemies as soon as you can. Use forced movement (Blast, Thorn Whip) to generate AO from allies and reposition enemies at your vantage. Minor Illusion to modify battlefield (covers, false gaps, ecc), Vicious Mockery to help ally, Shocking Grasp to disengage, Thaumaturgy\Friends as social tool.

Progression: At lvl5 you can get the infamous Devil's Sight + Darkness combo which can transform you into a walking nightmare of disabling madness, very hard to target. Lots of tactics here, disabling sight with plain movement is a powerful option, plus you attack with advantage; just take care of LOS of your allies. If you want more utility you can always get Rituals. Darkness is 1/day from Tiefling so you can also get a lvl 3 spell. While patron's spells are not that great, at lvl 3 you have 2 strong area disables (Fear and Hypnotic Pattern) and Counterspell, which is really useful if you are the only caster in the party.

Here is Lvl detailed progression:

lvl 1
Tiefling: +2 Cha, +1 Int, Thaumaturgy
Patron Fey: 1-turn Area disable 
Spells: 0 - Eldritch Blast, Minor Illusion; 1 - Hex, Sleep

lvl 2
Invocations: Agonizing + Repelling
Spells: 1 - Faerie Fire

lvl 3
Pact of the Tome: Vicious Mockery, Thorn Whip, Shocking Grasp
Spells: 2 - Phantasmal Force
Tiefling: Hellish Rebuke 1/day

lvl 4
Spells: 0 - Friends; 2 - Hold Person
Feats: Alert (from houserule 4th lvl)