Bard as a second class still allows you to off-heal with your AoE heal. Generally a Bard subclass won't be solo healing dungeons anyway, so you should normally have a Bard there using their Ballad skill anyway.
The other advantages of going Sorc/Bard are the skills you can unlock via Envoy's Path. You can have a Fire Sprite summon to fight alongside you (the extra damage is nice and it has a great health pool), use a party buff that increases evasion, and get a nice linear AoE (Like your Flame Impact on a longer cooldown).
GS_Tsuku - Bard/Ranger - Lv58 - Hydra