An average melee attack has +8 to hit. Also, forgot your magical weapon (DM Fiat).
Also, The Hound has pack tatics, 10 damage and knock prone.
The Shadow Sorcerer can Summon multiples Hounds each turn...
Its scary..
I am betting your fellow players prefer the careful fear/hyptnotic pattern after just a few times trying out the polymorph?
You might try using the Hound plus a bonus action Mind Sliver followed by a polymorph on the foe to turn them into a slug? That takes them out of the battle so you can deal with other foes first.
Bonus action to summon hound prevents bonus action (with Quicken) to cast Mind Sliver. Also the sorcery points are being burned through very quickly - 3sp for hound, 4sp for Twinned poly, 2sp for Quicken. Font could be used to convert slots to sp, but that also takes a bonus action (and you cannot go above your base sp for level so it can't be done in advance.)
At the normally played levels, this will be another of those alpha-strike strategies that are dependent on what you table is doing for long rests. If it's one encounter a day, it would be strong. A case that I could imagine in my groups games might be where the party is choosing the location and controlling the encounter, such as setting up an ambush for foes.
Actually, The Shadow Sorcerer is The most impactful spellcaster on right hands.
Every action can change the game. Its hard to compete.
The Aberrant Mind is strong. But, The Shadow Sorcerer remains competitive.
Other spellcasters cant compete with It.
I don't think any spell caster is more impactful than a Wizard.
The hound is ok, but it does not have enough hit points to be a really effective ally for very long. It's -4 intelligence save and +1 Wisdom save mean most opposing casters are going to render it useless in one turn, potentially with just a 1st level spell like tasha's laughter or cause fear. The other weankness is it rolls initiative, that really screws up its ability to coordinate with you and makes it likely that it will be eliminated before its turn.
You get the hound at 6th level and on the plus side it uses a bonus to summon it and does not use concentration. As an ally though it is not as effective as other summoning spells you can get by that level though, most notably Summon Fey, Conjure Lessor demons and Summon Shadowspawn (which odly enough the shadow sorcerer does not get).
If you compare these the Demons spell conjures a whole number of creatures to soak up attacks. The Fey and Shadowspawn can both cause charmed or frightened conditions with a difficult saving throw (the Fey as a bonus action for an entire minute with no save on subsequent turns). The hound can cause prone, but the save is a weak DC 13 and he does not have multi-attack, so he does not get much mileage out of it even if he causes prone.
