I'm not 70 so I can't go there but I can say this...
I initially rolled a Guardian, played him for about a month and was lovin' him. No one in my small guild had a guardian so I was unique. Since I have 2 young children I rarely get much time online so I usually just solo as I don't want to start a group only to leave 20 minutes later. After about a month the live update happend and I noticed everything slow down to a halt... I had been leveling doing quests in Splitpaw... before I could to the solo test all the way to the end, then I couldn't. I use to be able to viably solo stuff higher than me with ease, I still could but it took twice as long and I was almost totally out of power by the end of fight. This was not due to equipment as I have / had full Imbued Steel with an Imbued Fir Axe and Legendary Shield as well... when I inspect other Guards 7 levels higher or more I had more AC and often better stats... yet I couldn't viably play my class anymore solo...
Grouping was a totally different animal though. As I said I didn't group often but when I did I always instantly added to everyone's friends list and usually hear "you are the best tank I've ever grouped with." I was proud that I could go to Stormhold with all mages and a warden and no one ever got touched but me... Guardians are excellent tanks... just not a for me anymore.
So I wanted a change as I was disgusted with the change, I rolled an Inquisitor / Dominatrix and had a lot of fun for a few months leveling her up... She's a great healer and probably better than the guardian at soloing, takes about as long to kill but not nearly as risky... Healers have always been my secondaries though so I started getting bored.
My son who plays with me from time to time has a Paladin which is what I played in EQ1, DoAC and WoW (well a Shaman), I didn't like being a Ranger so I thought... what the @#$%, I'll roll a monk.
I rolled a Kerra monk about a month ago and even with my low playtime I'm at 23 already. It took like 5 days to get the Inq to 25, 12 days to get the Guardian to 29 and I'm at 23 with the monk and only 1 day played. My monk is a soloing machine, I can kill blues and whites all days long w/o really resting, just the 10 seconds left on my Thrust kick timer befor I can engage another. I have also been able to tank a little in BB and Stormhold, not like I could with the guardian but enough to get by with a group if they would listen and let me make sure I had sufficent aggro before they attacked.
Again, I'm not 50 or 70 but I've played a Guardian and a Monk into the mide 20s now and I can tell you that they are both good classes if played correctly, just depends on what you want to do. I would love to have my Guardian do have the DPS of the monk and I would play him or the monk be able to get half of my Guard's mitigation... but then they wouldn't be different classes now would they?
Play to have fun, if you don't like what you are playing, roll something else or try a different game... and remember it is just a game
Cheers!
Marb