That is the problem Gengar, you got your math wrong. That is not how it works. I used a damage calculator. It is perfectly normal, Reversal is not weak it is just that Mamoswine is bulky. You say Houndoom's HP was 10% then you may have been off by 1% and it be 11% so it would have 100 base power for it, not a 150. I ran the calculations for both. If it had 150 Base power then Houndoom would have taken about 2/3 of Mamoswines HP, if it had 100 Base power then it may have only done a bit less than half like you said. Did you do the math to find out how much percent or did you just guess?