In the MB3 epigraphs, Sazed strongly suspects that Ruin created the "eleventh metal" myth in order to facilitate the Lord Ruler's fall.
You have to remember that Ruin's touch during the Lord Ruler's reign was extremely limited. A very select few could be influenced, and not extensively. Ruin could not control Inquisitors while the Lord Ruler was in power. Even Ruin's over the Lord Ruler was fairly limited--sure, Ruin made him see things he didn't want to, and almost made him go insane, but it is by no means "controlling" him.
Ruin also influenced Vin's mom to make the bronze earring into a Hemalurgical spike into Vin so Ruin could influence her later. I'd think this has more to do with Vin's mother just being naturally unbalanced (similar to Zane), and thus is more susceptible to Ruin's touch, instead of Ruin outright controlling her.
If Ruin influenced Kelsier, it would not be "controlling". At most, Ruin could just create the seeds of the legend and that's about it. I just don't think Ruin would have enough power to influence Kelsier more than that. None of Kelsier's viewpoints gave any impression of being controlled from an external source (to my knowledge). Besides, Ruin is very smart, and so he would know Kelsier well enough to know that Kelsier will have the determination to overthrow the Lord Ruler without any of his deific meddling. Ruin just needed a slight nudge to give him the tool to win.