I need some help. All the monsters are a bit too dangerous. There seems to be no easy way on any encounter. Even if we see the monsters before they see us, they can implement plans and tactics to defeat us like taking high ground and so forth.
What are the main tactics to use in combat, other than a tank to soak up damage, and ranged units behind and everybody focusing fire on individuals to destroy them one at a time?
Okay, there are no tanks in DnD.
The main issue is coordination of effort. Work to figure out who the "main" bad guys are; as sometimes killing the boss makes the underlings run.
Yes, you are right, concentrate fire - fewer enemies mean fewer attacks.
Between turns it never hurts to try to hide; it usually doesn't work, but sometimes it does!
Be careful of getting in each other's way; try to plan ahead. Also it doesn't hurt to scan around, look and see if there are other enemies that might join in.
Anyone who can use a distance weapon should get one; doesn't matter if they suck at it - sometimes one "1 hp" attack makes all the difference.
Early on:
Bless
Cast things to screw up the terrain (grease, fire, acid)
Armor/protection spells
Heal early and often - spend some time getting a feel for when folks are "in danger" (I start looking/planning for heals if someone gets below 10).
