1. Which is exactly my point, Eldritch Scoundrel is a terrible hybrid class with no useful synergies between rogue and wizard.
I believe I just pointed out the useful synergies vis-à-vis survivability, and the rogue isn't lacking in any other department. besides those I've mentioned, Greater False Life, Blink, Displacement and Stoneskin also help shore up defenses. if you want more, high INT has obvious synergy with skill monkeys and Animal Aspect is an even bigger buff to skills. so spellcasting compensates for the Rogue's weaknesses and piles on even more advantages where he's already strong.
2. Who gives a hoot about Archmage Armor, a regular high DEX rogue with the proper feats can have good AC as well
good AC =/= best AC. in a game where enemies have multiple attacks with gigantic bonus, some 10 points of AC make a good difference. besides, wasn't your argument that ES was *worse* than regular rogue? the fact that regular rogues can have good AC but not quite as good as ES with Archmage Armor is not an argument that regular rogue is *better* than ES.
besides when your rogue is being targeted you're doing it wrong
in Wrathfinder, survivability comes in the form of AC and Woljif has higher AC than most other companions. sure, it's nothing compared to a cheesy Sacred Fist / Oracle with Crane Style build, but we're talking about his merits as a companion so he should be compared to other companions and not the PC. compared to traditional "tanky" classed companions like Seelah, Woljif has way higher AC potential.
3. Let's pretend that's true
it is.
then there's still no reason for Eldritch Scoundrel to exist because any other old magic user can just cast blur etc
other magic users have better uses for spell slots. and ES also gets Shield, False Life, Vampiric Shield, etc among many other personal-range spells.
you're only losing out on mirror image, which isn't that good anyway
Mirror Image is better than Blur, and maybe the best defensive spell in the game for its level. it's a minute-per-level duration spell that can soak in multiple attacks regardless of attack modifiers. what's not to love?
4. Wasting a level just to give him proficiency with better weapons (like kukris, of which there are much better ones than daggers) just so you have access to redundant self buffs is a bad deal.
regular rogues don't have martial proficiency either. again, how is it *worse* than regular rogue? you can believe the buffs aren't that great (and you'd be wrong, but whatever) but how is a "bad deal" to have them instead of nothing?