You can get a companion at any level. You just get a free one at lvl 16. Nothing stops you from buying one whenever you have the money. I had a cleric companion at lvl 8 on my GWF, helped a TON.
I had the opposite experience. I lvled a rogue to 20 in beta 2, and did the GWF in beta 3 and in the 4 clock towers I ran, I was 1st on dps in each of them, and sometimes by more than 20% from #2 (a rogue usually). The trick is to be the one clearing the extra spawn during boss fights (even though more often than not I…