Yeah this doesn't sound normal at all...
As @deviander said, I usually get +300 range at lvl 10 from putting on the ring.
I'd suggest making some characters for their links and getting 2 card sets to help your range. Also if needed, you can sell your evo 3 and buy some %dex and a better weapon or something? Getting only +300 damage at lvl 93 from a Evo 3 just doesn't seem right... It will eventually add up more to your range in the future, but you seem to want results to your range now.
I have like 4%dex and no %Att equips. I'm unfunded. I only have Luminous' link skill. And as for cards, I have TB, Kaiser and Bowmaster...(which isnt a good set of cards).
I don't know what is wrong.. 10Weapon attack only adds up 300-500 range and I am now lvl 100. Is there someone that could try equipping an Evo ring 3 lv 10 in the same conditions as me, and tell me how many range does it add up?
You do know that the stats and weapon attack from the ring you add to your character scales with other equipment/passive skill stats right?
Did you relocate your AP wrong or something? If you're at like Lv10 and/or don't have much for primary stats and weapon attack, then the ring won't add that much either. Don't be expecting the ring to add 1k~10k range when you're at lv10 with barely no stats/att to begin with.
There is also the damage formula for each class weapon type; 10 att may have more of an effect for certain classes more than others. It's different for everyone and how the game works.
Other than that, the ring is really nice if you have nothing else. It's still a boost and can be traded as much as you want compared to the other rings.
Everyone is pretty much on track. The benefits of the ring will increase when you have more %dex.
When you have more dex, your attack will be worth more, and vice versa.
Regardless, I would keep that ring because it will always have a great use!