1. Why use luck with darkside, it achieves higher damage on both base damage and crit damage from all of it's skills from using wizard, plus it's heal is locked to a long cooldown and needs that noticable higher amount given to wizard. The only reason I can think of would to be give the auto a higher crit damage since it's melee, but it's single target in a class primarily focused on multi target, that's also a magical class, I don't see how that'd really matter.
2. Oracle actually benefits in terms of damage from luck since it sometimes guarantee it's auto to crit, and it's only other source of damage is it's skill #5 edited timeline, while magical and while the class can increase it's intellect, there is enough of a reason to use luck in general use because while it's a support, people don't actually need that extra healing, much less that people actually don't use it as a support class as often as you'd think. Which is strange to me because it's damage is horrid. So i'd say not that luck is better, but that both wizard and luck are both fine for the class.
3. SC only gains extra healing from Wizard, and somewhat loses both DPS and some amount of mana regen, you lose like 30% that you would've had from crit modifiers with luck. or something like that. I don't think healing is really necessary to be quite as optimal as possible considering you also make everyone take 50% less damage
4. Collector has no good reason to use Wizard at all, it doesn't gain enough haste to make it's nuke or stun reliable enough due to longer cooldowns and weaker nuke. It remains way more consistent DPS wise if you use luck. However this is not necessarily true for VoT, where it can nearly stunloop, making it justifyable to run to full wiz. The difference between luck and wiz on both classes isn't too marginable but it's enough that I actually recommend different enhancements for both. Wiz/Luck for VoT and only luck for Collector, although that isn't necessarilly the case in PvP.