I finished up Borean Tundra today. Coriel is now 72. I did take a brief detour to Howling Fjord and did the first few quests so that I could do Utgarde Keep. I've done both Utgarde Keep and Nexus now, tanking as Retribution (in protection gear).
Tanking as Retribution isn't too bad, but you're definitely squishier, and sometimes your health can drop very fast. I'm thinking about switching to Protection, but I like Ret for general solo questing.
One thing about Retribution soloing is that it is much easier with Seal of Command. Seal of Blood does more damage, but the recoil means you have to keep healing yourself, and if you're not paying careful attention, your health can drop to dangerous levels. I skipped SoC at level 70, and I'd be questing, and then I'd look at my health and be below 20% for some reason (probably serveral SoB/JoB crits in a row). I picked up SoC at 71 and it's been much smoother.
The quests in Borean Tundra are well done. I especially liked the D.E.H.T.A. quests, especially the one where you free trapped mammoth calves, and they trumpet at you. (Also, the quest reward [G.E.H.T.A.] was hilarious.) The big cutscene quests were very well done, with a really nice integration of lore in regular questing.
I also really liked how the different camps had different flying options. The drakes from Coldarra, and especially the planes from the Fizzcrank Airbase.
The only negative was the torture quest in Amber Ledge.
Other than that, it was a great entry zone, and I'm looking forward to Howling Fjord, which is where I'm headed next.