Maybe because :
- the only Stam tanking trinklets are from 25 (the only good ones that works otherwise too), be it Juggernaut/Satrina, the one from Ulduar, the one from Sindra. The only good one in 10 is the Putri10 one (a nice change for once)
- not having access to 10/25 gear makes it impossible to mix up items from different settings to maximize potentiel and overcome the failures in itemization (things like too much hit/expertise or not enough at all on the items from one setting)
- Nearly all trinklets are better in 25, except a couple like WFS and Spyglass for a handfull of specs, all the other generally accepted good trinklets are .... from 25
Comparing ICC10 hm gear and ICC25 gear isn't right.
And once again STRICT 10 man guilds DON'T do 25 content, not even if it's old T7 content, it would make them lose their status of strict 10 man guild (at least on Guildox).
It's not hard to understand how it works when you use your brain, a little logic AND don't try to belittle the other's performance just to feel better yourself when you know you aren't on par....