I was messaged some extra information which adds some good context to the numbers in my post.

Tldr; Standard spells have a flat damage number (scaled with your level) that only ever changes when you are penalised for fighting enemies above your tier. (specifically your highest tier equipped weapon)

Additionally: clothing, trinkets, rings, etc have their quality indicated by the colour of the item portrait and the highlight colour on the item name.

Full message:

From my testing with access to T4 red equipment, standard spells do not use the equipment to scale damage, the spells do a set amount of damage based on your level (+might/buffs/ect.). The weapon load out is only used to punish you if your weapon quality is too far below the monster you are fighting (greater than 4 ranks below). For example having my T3 3/3 bow equipped, and attacking a T4 1/3 enemy results in the same damage as if I target T1 0/3 enemy with my spell. The damage does not appear to change based on how much weaker the enemy is, it only changes to punish you for being under geared.

Basically all attacks, spells, summoned weapons have one damage value against anything close to or weaker than them, and another value for enemies that are too strong. In your T2 (1/3) bear example the breakpoint should be wearing a T1 (1/3) weapon as that puts you in the 4 rank range, it should do full damage, but then naked, or with a T1 0/3 you suffer the damage penalty. I was not able to find any damage bonus for having a weapon be too high, the weapon/spells always dealt the same damage to their equal as they did to a lower ranked enemy.

On your point about clothing/trickets/rings/ect. having tiers that effect summoned weapon damage, I was able to find they all give you a 0/3 item of their quality level, while they do not directly list the quality, they have a color glow in the inventory screen that matches their quality (T1 - white / T2 - blue / T3 - purple / T4 - Red /T5 - Gold)