I don't totally agree with this. I do think myself a fairly good tank. With ilvl180 gear, I was able to keep hate from ilvl 205+ players, but they would always be on the cusp of taking back from me, especially if they had their rotations down pat. My flashes weren't enough to spread enough enmity in comparison to how fast they were hitting their combos. Gear differences can make it very hard to hold. If I had messed up my rotation even a bit, I definitely would of lost aggro on a few things. And honestly, may have it weren't for the fact that the high geared DPS were on point in burning the mobs quick enough.
Biggest issues I see if tanks not using their AoE to gain an enmity hold on mobs or simply not knowing priority in their enmity combos. I do tend to see MANY warriors who focus more on their DPS than their enmity and that can cause issues.
To that arboretum part, that's purely dependent on the teams capability, not just yours. A single mess up from a healer or tank could mean the party wipes. Those wasps do final stings and usually, right in succession. They deal out enormous amounts of damage, to the point where it simply seems like an insta kill half the time. If you don't burn the honeycomb within seconds of the tank going down, you wipe. I hardly call being cautious there to avoid the wipe (which takes more time) as bad. However, a decent tank should be able to tell whether or not their party is up for the task by the time you reach the honeycombs.