I agree. Combat needs some tweaks. Back when sword was the agro holder we seemed to have roles in groups. Then that was removed so everyone started healing. Now we say "screw healing, kill it ASAP" and its working so far. Sure groups wipe when there is a respawn or a bad pull, but that isn't a challenge really as much as it is an annoyance.
For odd balanced mobs the best example I can think of for a mob that takes too many resources to kill is the golem in GK. When I've killed it with a group with a cheese and a good power food, I use all my power, energize, and dig deep. Then I wait for energize to come back, use it and try to finish the golem off. Maybe this is a lvl 80 mob but killing that golem is "annoying"
I don't have any suggestions at the moment for improvement but willing to help with combat testing and offer feedback.