Hi there! Thanks, I'm really happy you are interested in the class!
Elemental burst is a feature that will be used pretty often, you see, it already requires you to hit the creature and I don't want to have too many rolls in one single attack action, it slows down the game. Also, since the damage is already lower than smites and smites simply add the damage to an attack that hit, it would be pretty weak with damage halved (or canceled) by a saving throw.
Currently it works like Sweeping Attack in the PHB, with the only difference being that it damages an area instead of one other creature. Since there is a precedent (and a place to lift the wording off) I don't think it's too strange to make it work this way.
If you still prefer to add saves I would advice you to raise the damage to d8 and make it so that winning the save halves the damage (this was my original design).
Permanent Runes is a level 20 feature, like the druid's "infinite wildshapes" it can bring to some exaggerated results, it's supposed to sound extreme and could need rebalancing to a gaming table that plays mostly at level 20. I don't think I'll change it, but I understand that it might be needed. Still, considering the extremely long casting time the best you can do with it is: become constantly blurry, gain darkvision, gain weak telepathy with permanent detect thoughts, become permanently large size (with all the problems that come with it), gain spider climb, give a +1 to a weapon (when you have already better weapons), etc. Invisibility, Mirror Image and other stronger effects have additional clauses to end the effect so they are not as permanent as others. Effects on the enemy are basically impossible to cast on them with 8 hours casting time, so this does not really apply. As you can see permanent level 2 support spells don't stack particularly strong effects, at level 20 when compared to what a wizard can do, it's hardly an issue.
Actually I just noticed that I didn't specify anything about spell slots, with the current wording you can cast a second level spell with a 5th level spell slot and have it permanent, while that's an issue only in very few cases, the intended design was that you can only use up to a second level spell slot to cast these spells.
Blood Bounty is strictly better than the warlock's dark one's blessing, but dark one's blessing is a level 1 feature and blood bounty is a level 3 feature in a half-martial class, and archetype features in martial/half-martial classes are usually better than archetype features in full-caster classes (or equivalent, like warlock). If it seems like that feature, in the context of the whole archetype, might make the archetype too strong, I might consider changing it to: "you regain hit points equal to the excess damage of your attack" or something of the sort. Yet I still think this will never get to the level of ridiculous sturdyness of a moon druid.
The damage plus condition is balanced usually by the "once per day" requirement and very very short duration (or pretty pointless effect, like the deafness one). In this case to see if it's balanced or not you have to look at the DMG and the magic weapons, because that's where these features are modeled from. Then again, it is supposed to have less annoying rolls during play. Some of these features add minor conditions that are modeled from cantrips, for example frost rune adds some damage and reduces speed by 10 feet, this is based on ray of frost that does its effect every time as long as it hits. Similarly Storm Rune is based off Shocking Grasp.
If you do add a saving throw I would advice to make the duration of the conditions a little longer than "until the end of next turn".
Thanks again for the compliments! Let me know how the playtest goes, I'm really excited about someone playing the class!
PS: I just noticed that I didn't update the file on the forum to 0.8, check if you have an old version of the pdf. The version that I copypasted on the second post in this thread is too much of a hassle to update and should be possibly ignored in favor of pdf versions.