I have many thoughts about warlocks and going to to review your homebrew here:
your reasoning at the start is quite right for the warlock, thee option available can be quite restrictive, especially because a good number of invocations are bad not worth taking.
For the artificer I disagree with not having enough options since "Replicate Magic Item" is actually over 50 options you can take multiple times, that said more bespoke options just for the artificer is still very nice
starting with each invocation:
- Survivor's Soul: first part quite useful to make healing more reliable , though I would include healing from magic items, too, I don't see a reason to exclude those. The second part on the other hand has such a narrow use case, you could remove it and you would not notice. I suggest removing the 1 minute time limit for the temp HP and also include being brought back from 0 hit points.
- Demolition Deviant: while a niche option, but it is nice and simple and I believe it can enable quite the fun builds where this niche comes in handy.
- Guiding Hand: a mix of Keen Mind and Dungeon delver is quite a nice idea, and the ability to find your way out of mazes is very flavourful as it is useful.
- Otherworldly Expertise: idea is good and generally good to buff an check when you need to, but that it requires an reaction to what generally already takes an action in the first place, is unnecessary and gives this invocation a bad feel to it.
- Fey Stepper: this one is good, a really nice package. I don't think you need to specify warlock spell slots.
- Eldtritch Claws: a really fun invocation that adds a nice amount of flexibility to a blastlock. Top tier invocation.
- Second Opinion: quite a flavourful and useful invocation, but the I personally find the name not fitting sounds like you go to another doctor, I suggest something like "Otherwordly Guidance" or "Ancient Knowledge" etc
- Deathless Perseverence: A really cool survival feature and love the idea of invocation that improve at certain levels, but a bit over complicated and written like it is a magic item. I suggest removing the limitation of one failed death save (since any damage will cause that) and the poisoned condition, and at 10th level it gets improved to something like you need more fail death saves to actually die, or gain advantage or proficiency in death saves.
- Bottled Banishment: a real fun one that turns your Genie Vessel into a pseudo Iron Flask.
- Voices from Beyond: is a really nice, and adds a concrete way to get help from your patron.
- Whispers of Danger: advantage against traps and ambush spells is great, the second half about ending surprised is a bit over complicated, I suggest "Additionally, whenever you roll Initiative while being Surprised, you can end this effect immediately."
- Elemental Shield: Damage immunity is already good, the second part reads a bit clunky.
- Seastride: really cool invocation, super useful whenever water is involved. Short and effective.
- Eldritch Resilience: damage resistance is always good, but maybe something regarding changing the damage resistance.
- Otherworldly Grasp: Telekinesis is really nice, but the restriction is feels quite harsh.
- Ravens Eye View: Really nice spell to get.
To the Artificer infusions:
- Elemental Weapon: basically the spell elemental weapon spell, nice even though artificer already get that spell.
- Self-repairing Armor: rerolling healing rolls is great.
- Ghostlight Gear: light that is only for allies is a great effect.
- Trekking Soles: a nice effect for shoes.
- Optimized Tools: a fine infusion, but you can actually do that with recreate magic item and choosing the tattoos.
- Accessible Armament: a useful infusion.
- Beacon Charm: useful for a tracking a target.
- Arcane Rifling: helps with not hurting allies, good.
- Armored Garb: turns clothing into mage armor, useful especially whenever you can't wear armours.
- Chameleon Cosmetics: magic disguise armour is a good effect.
- Agile Weapon: kinda bad for 50% of artificer because it is written to not work with extra attack.
- Armor of Deflection: denying advantage from range attacks is a really good and unique bonus.
- Diminutive Defender: more perma summons artificer.
- Alchemical Catalyst: double use for potion is really good.
- Oxen Armor: I am surprised this isn't part of Armor of Magical Strength, good.
- Lightweight Plating: removing disadvantage on all dex saves and checks is massive, extremely powerful.
- Aerodynamic Armor: extra speed and ignoring disadvantage on movement related checks is good.
in generally really good homebrew.