*** Title should be "How to make Dungeons and Bosses more engaging"
TL;DR: Dodging is useless unless you know where to dodge. Add an attack telegraphing system so people know where/when attacks are coming, but only give them just enough time to see and and gtfo the way so it remains challenging and interactive at the same time.
Borrow a little bit from The Secret World! Honestly, ANet has already done this with the dodge system, which when I started playing thought it felt EXACTLY like TSW's system, but I digress.
See those white lines on the ground? In TSW, those appear any time an enemy is charging up a BIG attack that will likely take out more than half of your health bar. Attacks like this happen frequently in GW2, as anyone who has fought a Champion Giant or entered a Dungeon will know. The problem with this in GW2 is these attacks are not telegraphed very well at all! Sometimes the enemy will pull their weapon back, sometimes it will even glow, but in all honesty you have NO IDEA where it will hit, so the only thing you can do is dodge back and run as far away as possible, hoping that is enough. Even worse though, is that sometimes these attacks aren't telegraphed, or sometimes they are so quick that you have absolutely no time to react. Casual players don't have a .01 second reaction speed to enemy movement; hell most hardcore players don't either.
The attack telegraphing system here is actually already in place for AoE attacks. Those little white and red rings on the ground when an ally or enemy drops an AoE is exactly what the game needs more of. Basically when you see them on the ground, you know right away to GTFO or you are going to die. Such dodging is what GW2 combat is entirely about, due to the lack of tanks and healers, so I think it would be a very logical step to take.
Now, adding in TSW's exact system IMO would make combat entirely too easy. This is why I'd suggest a few things:
1. Make the lines red, so they are A. harder to see, and B. easily classified as ENEMY attacks.
2. Don't do what TSW did and make these 'charged' attacks take 3+ seconds to cast. Any numbskull could avoid that.
3. At the same time, don't make them go off in .25 seconds either. Nobody can avoid that.
4. ADD MORE MECHANICS. Massive bosses that LOOK really nice are still boring as hell if they only have two simple attacks that don't hit anybody.
Adding this little 'hint' system would make combat much more fluid and not so aggravating, don't you think? One nice feature of this that I found in TSW is that it didn't make combat too easy (except on the afforementioned attacks that charged for 3+ seconds and you just had to sidestep out of them), but it made it more involved. This would be an EXCELLENT system for world raid bosses like Shadow Behemoth and Shatterer. Example: When they breath fire, instead of just burning everything directly in front of the mouth, have them launch fireballs that each get their own little telegraphed area, but make them fall QUICK so players have to react and get out of the way. This way 100 people won't get insta-gibbed, but people will still have to react to the boss and dodge accordingly. Use ANet's epic group of testers to determine what speed/size of these attacks would be too easy or too difficult, and there you go. Another example would be a large 'swipe' attack that takes up a certain area, but also attacks rather quickly. These lines would appear on the ground, and if you don't get out of the way you take a big hit and get knocked back. Sounds good right?