Scott Christian
Hero
In what world are you pitting 30 ho-hum, regular goblins, who are encountered separated from each other, against four 5th level adventurers? I don't know anyone who would design something like that. I mean, it sounds like you're just plopping a grid down and playing Warhammer.It's not a goblin clan of 3. It's the remaining 10 goblins after the party goes into the goblin cave, novas 20 of them down, then runs away to rest.
The surviving goblins have 8 hours to gather resources to combat an adventuring party that already killed the plurality of the goblin warriors a few hours ago.
You have to be fifth level to cast LTH. A fifth level "dungeon" with goblins would presumably have a quest tied to it. Such as, the goblins ransacked a halfling town and kidnapped some of the kids. Of course, there are the goblin dogs they rode in on. The hill giant, who is their task master. And the clever goblin mage and its buffed hobgoblin cronies, that forced the hill giant to get the goblins to put the entire plan into motion. There are probably two separate areas in regard to those groups as well.
That is an appropriate fifth level adventure.
Go in there and nova with captured kids around. Go in there and nova everything and cast LTH. Watch the hill giant come in and collapse the cave on you.
Honestly, if you are not playing with any narrative components or consideration to encounter design, your point is absolutely true. But, if you play with any DM that intelligently designs their encounters, it no longer becomes just a number game. It becomes an adventure.