I think his attack roll was 1d20+6. It was his damage he was wondering about. I can't say for sure. Obviously since theses are fan made rules they may not have been checked for balance.
I looked to the spells in the PHB though, because basically that's what this power is. From my research spells do not get the ability modifier all the time. Eldritch Blast, a cantrip for the Warlock does not get an ability modifier until at least level 3 and only if the player character chooses Agonizing Blast as one of their Invocations. At level 5 there is an extra ray that adds another die to the damage but requires an attack roll along with that extra die. Dissonant Whispers also increases damage if cast at higher levels and does not get ability mod damage. Looking at a few other Cantrips from other classes I see the same trend. Occasionally an ability mod gets added, but not often.
It makes me want to ask a developer about that. A fireball spell rolls 8d6 out of the gate, giving it a range of 8-48, average 24. A fighter with greatsword and a 16 Str (the 5th ed. version of high stat) has a damge range of 4 -14, average 7(but usually has multiple actions by 5th level when fireball can be cast). In the past editions spells usually had ability mod damage bonus, but there have always been complaints about casters overshadowing the fighters as levels got higher.
I guess they decided the way to balance that better was to lower the damage output of spells some. Plus the eye ray is an at will doing 2d6. 2-12, average 6. My character's weapon choice was a simple ranged meaning I do 1d8+3, range of 4-11, average 7.
So I guess in the end I think that no, no ability modifier added to damage, but that's OK because it is balanced against all the other characters.