There are ways to save quests to do in HW. In the initial 50-51 sets you get two breadcrumb trails that send you back to the western higher lands or back to cloud top after you quest in both initially. If you pick western highlands it leaves you all the 50-51 quests for your next class in cloud top to do. Also, around the 56 range several more breadcrumb quests that lead you to three different areas to get you from 56 to 57. You can potentially just do two and run a few dungeons to leave the third for yourself, then after you hit 57, more breadcrumb quests pop in Ishgard and there are even more that will pop for 57 to get you to 58.

I only did some of the level 57 quests that popped up in the various zones and largely ignored them, I spam ran the dungeon called the Vault a few times and did a few of the 57 quests in cloud top to get to 58. If you decided to do that as well, it will leave you several quests in the 50-52 range and the 56-57 range that will give you somewhat of an advantage to work with for your second class. If you decide to go for more than two though you'll end up having to grind it out. Hope those going in HW tomorrow or haven't progressed that far find this useful. =)