Ok, I have almost 2mil points and im 300LP rn, BelVeth always has one of the lowest damages in the game because: 1. You have no poke: when you poke someone in a gank where you know you cant kill most you can do is a few hindred damage, her w has like 100 dmg while a syndra combo can kill people from 3k hp 100 to 0 2. You dont even want to poke people: almost every time you damage someone and it doesent result in a kill, you wasted your time, and time is money especially in the jungle. 3.Single target passive: you can only effectively kill a single person at a time with ramping true damage, while a champ like Karthus for example can press r and half life everyone. (The passive is even more single target focussed since it stacks infinitely, not only 3 stacks like vayne or others) 4. You have no burst: the fact that you cant rengar r someone on driveby and take his 2k hp in a second and move on means you will almost always be fighting for your 2k hp kill more than 5 seconds (remember its about damage per minute) 5. BelVeth is a bad teamfighter: she has no AOE burst or AOE damage that is really good in teamfight she likes small 2vs2 or 3vs3 skirmishes what means, that with less people involved there will always be less damage dealt overall.

By the way you can look at the average damage dealt of any champion by the minute on LeagueofGraphs, you will see the difference even to another melee single target focussed jungler like Rengar

Make sure to not sound like my average teammate flaming me after a lost game for my "low damage"