I don't want to start an argument about this and it's not the purpose of the thread so I'll keep it short.
Trust me, I understand plenty. I'm well aware of Cu's warp spasm and Heracles as an archer. A strong servant in an non ideal class is still miles better than a weak servant in their best class. I'm not convinced that Cu is stronger in berserker than in lancer but regardless, in UBW when lancer Cu got to fight for the only time in the series without wearing shackles (the ones that don't come inherent with a sub par master anyway) he literally curbstomped Emiya. Forget what the adaptation shows, Cu tore him to pieces with low difficulty. Meanwhile Grand Order has Archer as 4 stars and Cu as 3. Meanwhile Heracles doesn't even need God Hand or Nine Lives to be stronger than every other non Gilgamesh servant in the 5th holy grail war. He's faster, and stronger, and more tenacious than any of them, and all he needs to do is stand on top of them and swing until they can't block anymore. Yet he's 4 stars and Arturia is 5.
There's a reason this game is known as Fate/Grand Fanservice. The rankings aren't determined by who's stronger, they're determined by who will net DW the most money. Which basically boils down to "Who's a saberface or has massive breasts?" Francis Drake is only the most recent iteration of the cycle, but it annoys the hell out of me.