It's not that you really need 1000AA at 71 as a warrior, it's that you need to earn those AA before you get too high level to find light blue old world mobs. This is assuming that you are going to be mostly soloing or moloing. If you box one or more characters, or if you have a really consistent grouping situation with guild members or friends, it might not matter as much to you.
If you level to, let's say, 80 or so with minimal AA, it's going to be a lot more annoying to kill the mobs that you need to kill to get AA fast. Not impossible, just annoying...and slower.
I went pure DPS AA (bypassing even things like CA/CS) until about 500-600AA. At that time, I was able to mow through light blue Luclin mobs without using a merc, and was earning really nice aaxp. Once you hit this point, you can earn your defensive AAs a lot faster.
Around 1000AA, you should have pretty much every DPS and tanking AA maxed for level. Then it's time to level up, picking up AA abilities that you unlock as you level (both ones you had maxed out, and new ones you didn't have access to before). I'm finding that I only need somewhere around 50AA per level to stay maxed in everything that is even remotely useful for a warrior.