I am also getting sales from dreamstime, fotolia and deposit. On deposit the prices are very low, you might want to consider sending files you feel comfortable selling at that price point.
Fotolia also has video subscription, but you must activate it. However it is for small web sizes only and you get very low royalties, not sure I can recommend it. On SS I have very good results with their footage subscription program,many sales over 20 dollars.
80% of my video sales are from pond5 and SS. So feeding them is for me the most important. All others are way behind.
On pond5 it took much longer than on SS to see regular sales.
Just my experience from my amateur portfolio. Hope it helps.
ETA: pond5 has quite a lively community where people also share recent sales. There is quite a bit of editorial content there. On SS the one editorial file I have sold twice. This is something you couldn't send to istock, so if have editorial video you can now make money from that content as well.