Guild Wars 2 combat has been quite controversial, some people think it is very engaging due to its actiony feel while others trivialized it as nothing more then spamming skills over and over again.
Personally I have found it very engaging and deep, It is different then other MMOs where as instead of focusing on specific skills and their "rotation" you have a set of skills that all have their own damage / conditions and boosts. In order to engage in optimal combat one needs to think of each of these as a tool and simply use the skills thats most appropriate in that instance. Facing the same enemy twice doesnt necessary mean the same skills can be used.
Its a bit complicated so I created this video to try and explain it as best I can: