How Arena boosting works — draft, not ladder
Arena is Hearthstone's draft format: you don't bring a constructed deck, you build one on the spot from cards the game offers you, then run it until your losses end the run. That makes the outcome a skill test in three places most players underrate — the draft (reading which cards make a coherent curve), the mulligan, and in-game decisions where a single misplay ends a run. None of it touches your rank: an Arena run is completely separate from the constructed ladder and from Battlegrounds, so a booster running Arena for you never affects your Hearthstone rank or your Battlegrounds rating boost.