If I recall the AI correctly from DS1, the mobs will attack first anyone who attacks them (and the party AI works much the same way) so a healer is less likely to be attacked than a combat mage who is dealing out damage. There's a bit of preference for the nearest opponent in there as well, so having a "tank" up front with heavy armor and a melee weapon makes them concentrate on that character as dangerous and near. If you're directly controlling that character you can make sure to whack as many as possible to get all the attention.
The range of the healing spells is more than the area of effect spells coverage, so your healer won't get hit by those if they stay back.
It's really a question of understanding the enemy's tactics, and picking the best one to counter it. If you know that they have a "return to base" strategy, it makes it easier to lead one away from the others, who will wander back home if they're not attacked. Some mobs will come for you solo if you hit them with a long-range arrow, but others will tell their friends and all come together. You need to find out and adjust.
You may also be able to find places where you can make ranged attacks on melee mobs who can't reach you, so you always want an archer or combat mage in the party to make use of those opportunities, but that can be a second-string skill most of the time.
If I recall the AI correctly from DS1, the mobs will attack first anyone who attacks them (and the party AI works much the same way) so a healer is less likely to be attacked than a combat mage who is dealing out damage. There's a bit of preference for the nearest opponent in there as well, so having a "tank" up front with heavy armor and a melee weapon makes them concentrate on that character as dangerous and near. If you're directly controlling that character you can make sure to whack as many as possible to get all the attention.
The range of the healing spells is more than the area of effect spells coverage, so your healer won't get hit by those if they stay back.
It's really a question of understanding the enemy's tactics, and picking the best one to counter it. If you know that they have a "return to base" strategy, it makes it easier to lead one away from the others, who will wander back home if they're not attacked. Some mobs will come for you solo if you hit them with a long-range arrow, but others will tell their friends and all come together. You need to find out and adjust.
You may also be able to find places where you can make ranged attacks on melee mobs who can't reach you, so you always want an archer or combat mage in the party to make use of those opportunities, but that can be a second-string skill most of the time.