Of course, many encounters can only be overcome by knowledge of the encounter - the Curator, Nightbane et al - and a degree of effort is needed to familiarize yourself with the fight before victory can be assured; I recall when both Moroes and the Curator were pains to do but now, thanks to knowledge of the encounters (and gear) they're fairly routine.
Not so encounters like Blackheart the inciter (with a very high random factor) or my current pet peeve, Kargath Bladefist (damn those random charges) which can be very frustrating as a random factor wipes even a well-equipped and prepared group.
And then there's the windmill. No matter how much you analyze some encounters (such as the Black Stalker in heroic Underbog), killing the target quickly is perhaps the best solution (and in fact over-analyzing things is a recipe for disaster). We call this "windmilling" (i.e. run in and hit the target) as explained in this educational video:
Of course, many encounters mix these up - a random element with a bit of windmilling, or a scripted encounter with some random aspects, but its scary that (in five mans at least) sheer, unadulterted aggression is often the way forward. The gauntlet in Shattered Halls is a good example - slow and sleady is a war of attrition the party will loose, but blasting through them (using pally-tanking to hoover up the mobs and then liberal AOE) is scarily effective.