New Armorer multiclass suggestions

I am playing a level 7 Armorer artificer dwarf originally intended as the team's tank with sentinel at lvl4, plate armor + shield practically always in guardian mode. Team was me, a BM fighter, Assassin rogue, Evo wizard, and hexblade warlock healer spec by dm.

We were all given artifacts level 1, mine being for tanking (temp hp mostly and now at level 7 can once per day dispel magic) while the others got magic weapons eg 2d6+2d6 lightning longsword for the fighter.

The wizard player left. my damage always feels crappy compared to rogue or the fighter unless I get high rolls with both the attacks and they miss all of theirs (sad).

Will be changing to the new version but it feels like the whole class and the subclass are not really improved even dreadnaught they kept the too little too late damage bumps at 15 from UA)

Was thinking to stick to armorer till level 9 for the +1 attack/damage they now have or lvl 11 for spell storing but maybe multiclass would help make the character feel like a threat the enemies would focus (so i can tank logically not because the DM may focus me as i am intended to be the tank) and because the higher level and capstone dont feel good.

What would be good options? Thinking one of the rogue/fighter/wizard. Perhaps at level 9 so i can get my int to 20 on level 8.

Stats are 

STR 17 (but got also gauntlets of ogre power so 19) , DEX 13 +1 (sentinel), CON 20, INT 18, WIS 14, CHA 12 (rolled method. DM told me to put 17 in STR over DEX as dwarfs arent nimble but bulky - even he has forgotten about that now)

First, I just want to call out that damage per round is not the only way to be insanely valuable in a fight. Artificer is a force multiplier rather than a damage machine, though it can do plenty of damage. Your rogue especially is grateful for every hit you absorb while tanking.

What spells do you have prepared? Which infusions are you using? These are a big part of your tactics and power budget. If you don't have a homunculus up, you might consider it - it can do some damage but the flanking can also be super valuable to give your other party members advantage. Your rogue in particular can benefit from a mobile friend distracting your enemy, giving them sneak attack on every hit. Set it to dodge and you don't have to keep commanding it - either your enemy wastes an attack on it instead of the rogue or it won't be attacked.

Your thunder gauntlets (if you're a Guardian) focus attacks on you, giving your other party members more leeway to do their damage. And Extra Attack is pretty great. The armorer in my party paired them with the Booming Blade cantrip.

You have Shatter which is a pretty good AOE damage spell. Thunderwave isn't bad either. Check out the other 2nd level spells especially - heat metal and vortex warp are two that are fun in some combats. Kinetic Jaunt lets you go anywhere on the battlefield without attacks of opportunity, which is actually much more fun and interesting than you might expect. Aid can be used as a remote heal to get your comrades up and running. Invisibility can get you out of a fight altogether. 

I'm not sure why you're buffing Strength on this character - your attack modifier is Int.

As I said I wanted to put it to dex but wasnt allowed. spells I primarily used thunderwave and shatter.

Infusions Enh Def on armor + repulsion shield , Homonculus, or Enh Def on shield + Resistant armor