well, its a nice boost overall. it doesnt really turn the tide on its own, it just helps.
It really opens up the ability to play a creatureless spellless deck. Poison, Couple of these, some shards, maybe a scorpion for neuro conversion. .i8t would be slow, but hard to counter all the ways damage is coming from. Add in spells and creatures you get a lot of different directions damage is coming from. unstable gas and catapult are good, but a nice permanent, that you can play that deals some damage on its own is rather 'needed'. i have looked at things like a cannon, or curses, but this makes a nice other card. Did you notice that you named mostly darkness and light cards in your example, why not have this in a fire deck, or an aether. Damage would be in between creatures and weapons, and is not a spell either, im not sure what shield would affect it, Id think it is physical damage myself.
Its like, why take a Druidic staff, green shards are better. Well, if you are playing mono green Druidic staves are ok. Why have this card, because it would make a nice addition to a lot of decks, but not so many it would always be used. For damage, creatures are better, for healing, a Green Shard, but its right in the middle there, nice and handy in a lot of decks, but not an 'always take'.