I did the Diessa Lowlands quests when I was about the same level as you (on an E/Me). They were extremely challenging, I won't deny that. It didn't help that I was new at the game and didn't know my way around anything. But the thing is... I enjoyed it immensely. I thought, now here is a real challenge. Gotta really earn those massive XP rewards.
So I kept at it and eventually finished them. I was at 60% Death Penalty by the end of Althea's Ashes and painstakingly dissassembling the Charr teams one by one reminded me a lot of Commandos.

(It was easier than Commandos actually. In Commandos you couldn't afford to leave bodies lying around, or to approach the groups in any order.) It's outstandingly good practice that you will treasure later. It teaches pulling, flagging henchies, strategic thinking, all sorts of things.
On another (possibly unrelated) note, I think it was the Diessa quests that really opened my appetite for the game. I started exploring a lot, even ran myself all the way to Lion's Arch, skipping the missions. I'm very glad I did it. IMHO the missions take you over the mountains way too fast. There are entire areas and outposts that you'll never get to experience or even see.
They're sad desolate areas (Ascalon after the Searing or cold mountain passes) but there's a wild, harsh beauty to them as well. The feeling is incredible (the artwork, the detailed landscapes, the sounds, the music). Little things, like seeing the first signs of snow and the first juniper bushes after the Ascalon desert that made me realise how much I missed Pre. It's probably the memories of that trip I'll treasure most of Prophecies, the excitement before I got jaded.
Not to mention you may need to do it someday anyway, and it pays to have previous experience. You may want to run a buddy from Ascalon to Lion's Arch, or you may want to bring a Factions or NightFall character to Ascalon.
Taking on higher odds as a low level character teaches you a lot. Some things are simply impossible (for example, I couldn't get out of Beacon's Perch on the Droknar side at that time, I always got pulverized) but you learn WHY they're impossible. And I did get to Lion's Arch, and to Elona, and Cantha, and Eye of the North, and did a lot of secondary quests around them. So what I'm trying to say is that you'd be surprised what you CAN do if you persevere. But you gotta use your head too, read build advice, read the wiki hints for all the quests and areas you're in, think about what henchies to use, how to approach mob groups.