You are absolutely correct about some of the combat situations, particularly if you don't find high ground and use sight lines, stealth and ranged attacks to nullify the enemy. Of course if you do that the enemy just stands around saying nasty things while you pop out, snipe and then hide again. Those troll things are ogres and they are challenge rating 2 by themselves. Challenge rating gives you and idea of encounter difficulty for a group of 4 PCs. Challenge rating 2 is a good challenge for 4 2nd level players, 3 ogres is a deadly encounter.. it's challenge rating 6. So when people are tactically beating it, generally speaking they are exploiting the terrain and AI stupidity to do so, in table top they would be very unlikely to survive, much like all the people having issues with combat.
