(For those of you following along at home, the following is the player talking to his DM. My intent is to "think out loud", rather than "be obnoxious".

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With enough mobs this is definitely doable, but remember the DM is a bit constrained to do much of this given the XP budget.
True. Of course, if the encounter is in waves - with some expectation that some monsters won't even "make it to the party" - the XP budget could be the same while the number of Bad Guys is larger.
...looking back the initial goblin encounter in the ruins was set up this way....
True! I'm just thinking about movement and position here: in that first fight, movement mattered much more. For me at least, that made it more fun. YMMV!!
I'm just not
that good that as the DM I can think of all the cool stuff that players
might or
could do and give all kinds of hints or even spell everything out for them. IMO players have to help think outside the box, perhaps even more than the DM, and see what they can do to turn nearby terrain to their advantage. With beginning players sure you need to spell it out and/or drop hints, but veterans? Really?
The issue is familiarity.
Since we (the players) don't know how the world works just yet, we don't know what options are open to us. Even experienced gamers have this obstacle, although (admittedly) it's smaller than for newbies.
Actually, once the Controller Spitting Kruthik was killed the others would've fled back to their nearby lair and been easy to kill, essentially ending the encounter.

That hint (pardon me for saying so) wasn't all that obvious.
Moreover, to get to the "queen" we needed to get through the soldiers and minions, then climb a cliff with a difficult Athletics (thus Str) DC. It's neither practical nor smart to disengage the melee types once they were pressed close in on us, and doing so while trying to climb seemed....sub-optimal.
...but all of that is Monday-morning QB-ing. The point is that we either didn't have or didn't know about other "dynamic terrain" options.
And FWIW, it's cool to have combats were the only option is to stand there and take it.
"Hold your ground you yellow-bellied maggots! Stand there and take it, and give back worse than you get! You don't get to die until I see ten of them bleeding at yer feet!" I think everyone agrees about that. I'm just "thinking out loud" 'bout how to give PCs "dynamic terrain" options, and what might make that easier.