The choice varies quite a bit. There are a few gimmes: tasks which don't involve any combat at all and can be knocked off in a matter of seconds, things like throwing a handful of items into the mystic forge or visiting a vista, for example. Then there are the easy ones that take a bit longer but pose no problems, mainly the various gathering options - foraging plants, mining ore, chopping wood.
Sometimes there's an option to attend an "Activity", one of a handful of mini-games, accessed via an NPC in Lion's Arch. That's another gimme in that you get credit for being there, not for doing anything, but you do have to wait for the event to run its course, which can take a few minutes, especially if it's Southsun Survival and some ingenue actually tries to survive.
There's always a full set of dailies for structured PvP so that players who do nothing else can get their quota without bothering the rest of us. In PvE there's often a World Boss on the list, which is easy enough but which can only be done at a specific time and there are a couple of Fractal dailies which, annoyingly, often seem to crop up together. The option to complete four events on a specified map is usually one of the most time-consuming, especially if the map in question is Snowden Drifts.
A good day is two gimmes and an easy. I can knock those out in five minutes or so. An average day is one gimme, an easy and something more fiddly that involves a deal of running around or waiting for events to spawn or timers to run down or which needs a zerg or offers the risk of being ganked and having to start over. An average day can run anything from 10 minutes to half an hour.
Very occasionally there's a horrible day with nothing easy at all and several, like the Fractals, that I won't even consider. The longest it's ever taken me on one of those days is an hour and a half. And then, of course, I have to do it all again on the second account. And then yet again on the third.
This is why my highest character on my third account is level 60 and holding. I am keeping him back deliberately so that each day I get a wider choice of dailies across the board. If I get Frostgorge Sound events as a PvE option for the first two accounts I know I'll have Wayfarer Foothills for the third. If the 80s get Claw of Jormag the young 'uns will get The Frozen Maw. It's more fun that way.
It makes me wonder what's going to happen when Heart of Thorns arrives. Nothing's been said about how it will affect dailies, as far as I know, but it's bound to have a significant impact. Players won't just be differentiated by level any more but also by whether or not they have the expansion registered to their account.
There are a lot of ways that could go. It only affects PvE dailies directly, since WvW and sPvP players will all get the Desert Borderlands and Stronghold maps by default, whether they buy the expansion or not. We could therefore keep the same number of dailies and some or even all of the PvE ones could mandate HoT zones and still no-one could claim they were being locked out completely.
That would appear quite harsh, even so. A softer option would be to expand the PvE choice from four to six or even eight, mixing expansion and non-expansion maps, or we could have two separate PvE sections, Pact Tyria and Heart of Thorns, or we could go back to having set tasks but freedom on where to complete them. Or they could revamp the entire daily system for the fourth time or do away with it altogether.
Whatever ANet decides to do I imagine I'll acclimatize but precedent suggests dailies will be less fun that they used to be. So far my favorite version was definitely the original, where we had the same dailies every day and a free choice of where to do them. Second-best was the next iteration, which brought in a rotating choice but still left it up to the player to pick the venue.
The current version is the worst of the three but I still get a lot of entertainment out of it. I'll probably manage to find a way to go on enjoying whatever they come up with next.
Whatever they go with it's a fair bet I'll be ticking off as many boxes in the old world as I'm allowed. And I plan on keeping one account with no level 80s and no Heart of Thorns to give myself the best possible chance of getting the kind of dailies I most like doing.
Very easy ones.