I play all 3 roles on a controller on PC so it's not that hard. As a tank, you set your filter to Enemies and cycle through them. The aggro'd mobs list will highlight slightly which target you have your target on if it's not a focus target. As a healer, I do the same thing with filter. Leave them on enemies and use up + down on D-pad to target party member. It also helps to rearrange your party list for priorities so you can get to some members faster like tanks or melee dps. This can be done by going to party windows, click X one on the one you want to move, up and down on D-pad and click X again once you're done. You can click up twice to get to party member no. 8 as it is faster that way. Thing is, you need to disable the top half of the filter configurations windows (the part about weapon sheath or drawn) and enable the customized filter.