Yes, earth magic teacher (Alicia - art done and a patreon preview) will be in the next 1-2 updates. Mana Blade was kind of experimental, I'll add more to it over time depending on initial feedback, especially if people liked the mana juggling aspect of it.
Well I got to say I rather enjoy it. I always enjoyed going for a Spellsword build, but I always worry I might run out of mana for the skills, but Siphon Strike managed to fix that worry. Also the base skills for the Mana Blade really seems to synchronize with the other elements. However, I always have trouble wether to go for Insight for extra damage or Agility for evasive and fast tactics. I hope that Mana Blade gets more work done on it.
You're exactly right - the base skills offer a decent baseline kit and synergy with the special stuff for each element!
Mana Blade already gives some free defense/resist penetration, so I think it's safe to go for Agility/Vitality (defensive) or Focus/Dexterity (crit) depending on whether you want to be tanky, focus on spells, or focus on skills. Cuz you still have access to the full Longsword skillset too.