Yep, I was just typing a reply then saw you'd posted. I'm surprised the capacity of the derailleur is so low. My tiagra mech has a capacity of 39 by comparison!
I wonder how the pros manage to use 28t cassettes with DA mechs?
Longer cages no doubt.
I ran 50 34 and 11 28 for majorca, didn't use the 28 from memory, long steady climbs!