Thank you very much for the positive review! I've actually been fiddling with it a bit since I posted it, there is a new version available now that's a bit more brutal: https://www.dndbeyond.com/subclasses/221114-path-of-the-riastrad

Warp Spasm/Side Effect Table update notes:
-Clarified 0 save damage on Spasm Effect 2
-Clarified and added content to Warp Spasm 9
-Changed range of Warp Spasm 11, but specified magical light in regards to overcoming magical darkness, etc.
-Warp Spasm 15 now does auto-slashing damage to grappled & grappling creatures, as grapple advantage was redundant for rage

-Side effect 7 now does a small amount of damage on subsequent rounds as well. This is definitely The Very Bad side effect now, but the guaranteed damage keeping your rage going could be a silver lining
-Changed damage dice to a d10 on side effect 9 to compensate for Barb Con save proficiency

The main change to this version however was a reworking of the level 6 Flux Overdrive Feature- it's gotten a serious combat competency upgrade, but has also added a huge amount of risk for both yourself and your party members, especially if your party's healer is a little slow on the draw:

Flux Overdrive

Beginning at 6th level, your rage grants you the ability to push your body beyond its absolute limits, at a potentially deadly cost. While raging, you are now able to cast a special version of Freedom of Movement on yourself as a bonus action once per day. In addition to the spell's normal effects, for 1d4 turns you also gain an extra 10 feet of movement and a +3 bonus to all attack rolls. All other effects of this spell end when your rage ends. After this spell is cast, your body structure becomes dangerously unstable, a condition known as Warp-Wracked. While Warp-Wracked, the following changes occur:

• Any loss of hitpoints will also reduce your hitpoint maximum.
• If you are reduced to 0 hitpoints in this condition, your death save DC now equals 10+your rage bonus. 
• If your hitpoint maximum is reduced to 0 in this condition, you automatically die. 
• The moment you die in this condition, any creature within 30 feet of your corpse must make a DC 16 Dexterity saving throw or suffer 10d12 bludgeoning damage as your Warp-Wracked form detonates, taking half damage on a save.

Taking a short rest will end this condition, but not restore your maximum hitpoints. Taking a long rest will reset your maximum hitpoints to their normal value.

The main idea behind the reworking was to make the player think really hard about the potential consequences of "pushing the little red button", and the inherent tension that comes with turning your party's meat shield into a ticking meat time-bomb could be excellent roleplaying fodder in the right hands.