According to D&D rules you can't cast both a bonus action spell and an action spell at the same turn, unless the action spell is a cantrip.
When multi-classing will be here and people will combine this concept with the Thief that can use 2 bonus actions in a turn it will be really crazy.
Also, it's not fair that spells leave behind lingering effects without tying up the spellcaster's concentration. The idea that my spells keep burning the enemy while I am concentrating on something else is not how 5e works. Also, in a way such spells become unpredictable. In D&D when you want to control the battlefield there are dedicated spells just for it, like Wall of Fire, or Evard's Black Tentacles, not every spell need to leave behind a zone of damage, it makes the game very unfriendly to melee characters. Not to mention that it really weakens the evoker that suppose to sculpt his spells around his friends, but in BG3 he will leave them stranded in a sea of slippery ice, or burning fire.
Last edited by Zress; 09/10/20 09:10 AM.