There is a lot of pressure placed on the tanks and healers. Once you are used to the mechanics, you will notice some fights place more emphasis on one or the other.

Also, you will notice the classes were designed starting from lv.50 and then the developers spread out the abilities to the lower levels. This means that the class feels complete at Lv.50, without any wasted skills, but you will sometimes feel lacking in the early levels.

I would recommend you pursue leveling the tank or healer of your choice, and ignoring the criticism. You are on a friendly server and have players willing to help you.

If you are considering a dps class, Arcanist can be leveled and grant you simultaneous access to Summoner (dps) and Scholar (healer). There is a fair amount of pet management involved in it, so it may not fit your playstyle. Most players like Bard, and their use of buffs to support the party is useful. Between monk and dragoon, monk tends to have the easier combo. Playing either of the melee dps will introduce you to dodging and give you a front row seat to learning tank movement in the game.

I hope this advice helps you and I'll see you in the game hopefully. If you need any advice, help, or equipment, feel free to ask.