Hi there Macabre, and welcome back.
1) Mind spike stacking extra crit on MB does not exist anymore. Part of the functionality is in a Major glyph, which allows a non-instant mind spike (can't benefit from From Darkness Comes Light, a T3 talent) to reduce the cast time of MB by 50%, stacking twice to make MB instant. Its not worth taking for PvE in nearly all scenarios, I safely ignore it.
2) If you take Divine Insight (T5 talent) your MB will periodically refresh its cooldown early, be instant cast, and cost no mana. It triggers as a % chance from SW:P
3) No dots are automatically refreshed anymore, but you don't have to keep Devouring Plague up on the target. Its been changed to a bursty-style dot with low uptime.
4) Wands are now considered the same as a dagger or 1h mace. It slots into your mainhand and has a large amount of spell power, allowing the use of an offhand item.
5) You can take a major glyph to allow that again, but it is not a dps boost. SW
without the glyph has had the backlash removed, but the glyph adds that back in. The plus to that is you can still use it to break from Poly effects in PvP if timed right.
6) If you take mindbender, it will replace shadowfiend. It does about the same damage (unless I'm mistaken), but you can use it 3 times as often. Mana regen is altered to make it similar to the other talents in T3, to balance healing.
7) Yes, Vamp Embrace is now a pseudo raid cooldown. You don't have constant trickle healing anymore, but the new VE is fairly powerful when used appropriately. (Its great to help healers on phases where the boss takes increased dmg) Remember that the healing is split, so in a large raid it will heal a minor amount per player, but solo or in a small group you can bring a team to full very quickly.
8) Apparitions are changing slightly in 5.4, but their functionality stays the same, in that they're essentially passive. They trigger at a 60% chance from SW:P critting, so as long as you have a SW:P active you will still see the shadows of your mind assaulting your foes. (They deal nearly trivial damage, but I still think its a cool flavor effect in pvp, until next patch)