If you let Brand consistently hit you with a full combo, then you need to practice avoiding skillshots. Yes, it is fairly difficult to avoid, I don't deny that, but his damage at the current point is far lower than it used to be, unless he manages to consistently hit you with three spells in a row. Yes, if you die to him even once, he'll become difficult to deal with, but that is generally the case with most champions, especially mages. Brand snowballs very well, so that is simply a matter of NOT feeding him early.
As for how he kills people who ganks him, Brand was infamous for that even before his rework. He's a significantly less capable duelist now, although if you're bad at avoiding skillshots then yes, he will steamroll you.