I think the headband of intellect is meant for rogue and fights, so they can take the eldritch knight and the arcane trickster and be as good as the wizards.
Eldritch knights and arcane tricksters are not meant for lobbing spells at enemies(minus cc), that’s what a wizard does. They are meant to augment their fighting. Eldritch knights with abjuration, arcane trickster with illusions+ Magic middle never misses, don’t need intellect at all for these.
You are right that to balance things out they should add objects that help all the classes. Not just +1 to hit, but also magical robes (I found just 2), more belts, objects to set other attributes to 18, etc.
You don’t need to wear robes. Dwarves and gith get light/medium armour. Or get a talent at lvl 4 for light armour. But you’re armour should be shield/blurt/mirror image
But balancing loot is complicated. Right now I think rogue have it best. Even the magical weapon you craft is designed for them.
what magical weapon? You can craft several weapons. From a 2h, sickle , spear for example.
clerics are severly handicaped.
not at all. You can use any weapon you want. If you want proficiency choose a race with those(short swords/long swords elves, dwarf axes etc). Clerics can use simple weapons, and there’s a hatchet from the halfling merchant that does burn on hit. Or you could literally use a torch and do 1d4, 1d4 fire lol