I play a warlock, and i never see best in bags recommend i stack any traits. It seems to want 1 level in as many things as possible and doesn’t account for stacking. If i look at blood mallet, it will show clearly more dps by stacking a specific ability than choosing another that ask mr robot says i should take instead. Is ask mr robot able to take into account stacking at all?
Yes, we take into account the fact that you can stack traits.
If you post the string of data that you copy from the addon to the website, we can look at your case in more detail.
Without seeing the specifics: our site is much better at finding a custom solution optimized for the gear that you actually own. Static sites like blood mallet are never going to be as good as something based on your actual inventory of available gear.