That makes sense to me, after about 3 months of putting down ~$160 you got 10 unique Legendary heroes. According to How much should I spend?- HotM cost, and odds, analysis, you’re a bit above average with luck but in the same range of the median.
I’m a cheap player, I get money from Google Rewards. That’s usually what I save up myself, covering the difference myself (usually ends up being about $1 - $3). So far I’ve got Khiona, Red Hood, and Mitsuko in that order, below average of the median of 6, but around that ballpark too.