Firstly, the two Jobs on Arcanist (ACN) are two totally different roles - Summoner (SMN) retains ACN's DPS role and just changes Carbuncle to 'egis' (minature Primals), hence it's style of play is pretty much the same as ACN. Scholar (SCH) on the other hand, is a healer, and Carbuncle is replaced completely with fairies who act as a kind of automatic healing bot. SCH is much more difficult to play as the fairy's AI is somewhat unpredictable, however their healing powers are potent in the hands of a skilled player. So yeah, if you go the SCH route, you will be a healer in a party. Also it should be noted you cannot freely switch Jobs in a dungeon or raid - you will have to choose one or the other before entering.
And Silentj, don't listen to stupid players like that - especially for those that 'want a fighter'. Conjurer/White Mage (CNJ/WHM) is a healer plain and simple. These players are most likely just wanting to speedrun the dungeon for their stupid tomes and anima crystals, and forget the whole reason those bonuses are even in the game is to actually help new players like yourself, so don't think you're the problem, because you are not, it is them.
If they're too lazy or impatient to understand that, just ignore them and move on, don't let them waste any more of your time, and especially don't let them ruin the game for you.
