Since I've been spending an awful lot of time on MP compared to SP I kind of understand what you mean.
All the MP classes are a mish-mash mix of the trees from SP.
Easiest way of telling where an ability if from in MP, is by simply looking at the symbols. They are color coded the same way in each ability/spell tree in SP.
Ex.
- Knight Enchanter: blue BG(background) and yellow FG(foreground)
- Necromancer: purple BG, black FG
- Rift Mage: moss green BG, and white to orange FG gradient.
- Weapon and Shield: grass green BG and golden/yellow FG
And the special cases for the Focus abilities, which all have black/brown BG, and yellow FG and corners,
And from MP the Focus ablities you should know is:
- Firestorm: SP Rift Mage (from MP Elemenalist)
- Rampage: SP Reaver (from MP Reaver)
- Counter Strike: SP Champion (from MP Legionaire)
But the key points of your question is:
Can you make an Elemenalist in SP equivalient to MP?
Answer: Almost, but no. Firestorm and Stonefist from Rift Mage, but the Death Siphon comes from Necromancer.
But instead you have access to 4 more spellslots, Rift of the Void (Arcane Warrior from MP)
Can you make a Necromancer in SP?
Answer: Yes, I think she uses everything from Necromancer tree and the common trees. Additionally you get access to Firewall, Barrier and the focus based spell: Haste.
Can you make an Arcane Warriror in SP?
Answer: Almost but no, you can have Fade Cloak and Spirit Blade from Knight Enchanter. But not at the same time as Rift of the Void in the Rift Mage tree.
But instead you can cast barrier on demand, get the reduced barrier decay. And instead of Rift of the Void you can use Static Cage and Disruption Field from the Keeper to almost the same effect.
And in all cases above, you mentioned healing to increase survivability. Try using "Heal on Kill" effects from items. I think even in MP you can craft them up to 8% I think it was. Not as efficient as Death Siphon or Rampage + Dragon Rage, but I find it especially useful when I play AW in MP. (Cloth Offensive slot)