Account binded gacha?

If you do enough pulls, statistically speaking you should have an approximate number of pulls per servant. I doubt that the gacha can be manipulated by a player's account. If you're using the FP gacha to pull 3* servants, you're not going to pull many 3* servants, let alone Robin Hoods. You would pull a lot more Robin Hoods if you pulled from the story gacha.

That's not to say that the gacha can't be RNG manipulated. Getting a super success when feeding servants or CEs tends to increase the likelihood of pulling SR and SSR cards.

Also, I think having favourable pull rates for certain accounts would be illegal. FGO is a game that already has greater scrutiny for its lower rates and higher costs.

Can't say I've seen any trends with my pulls. The only class I've ever had bad luck with was Assassin since, asides from Summer Shishou, I only got my first other gold Assassin (Camilla) last week despite having played more than a year. I've been making do with Kotaro, Cursed Arm, and Kojiro ever since I started.

Other than that, I've had mixed successes so I doubt each account has some sort of hidden status that determines what Servants are summoned more often or what Servants are harder to get.

It's most likely just personal luck, or bad luck in the case of those who have next to non-welfare 4* or 5* despite playing for months.

Also, if I remember right, the chance of getting a 3* Servant in the FP summons is the same as the chance of getting a 5* in the SQ summons. Or something like that anyway.

If you're talking about the FP gacha, from my statistics (now up to a sample size of over 1000 rolls), I find:

1* servant: 9.1%
2* servant: 4.9%
3* servant: 1.1%

So, there's roughly a 15% chance of getting a servant. For spending 75k FP, that's about 375 rolls, and thus on average you would have gotten 56 servants, of which 34 would be 1*, 18 would be 2*, and 4 would be 3*.

Considering that I count only 6 1* servants, 2 of which are assassins, I'd expect you would have gotten around 11 1* assassins, and probably 5 or 6 copies of Arash, the only 1* archer. There are also 2 Berserkers in the pool, so I'd expect you to have gotten 11 of those as well. The last possibility is Mozart (caster), who you should have gotten also around 5-6 times.

There are no 2* archers or 1* or 2* sabers, so that cuts down the representation of those classes from the results as well. And there are 3 2* assassins out of the 11 possibilities (with no other class having more than 2), so they show up the most from the 2* results: 5 of the 18 should be assassins, with 3 each from lancer, rider, caster, and berserker.

I count around 30 or so 3* servants in the pool, so the odds are pretty low of getting any specific ones.

So, I think you are probably just seeing results due to the fact that there are more 1-2* assassins than any other class, so they come up more often than any others. Berserkers aren't far behind.

I heard that saint quartz gacha is based on random numbers that are generated after some time (1 sec or less) some people posted photos how they rolled at the exact same time and get the same rolls.