Seems to work well for me. People having problems need to note the mobs they are fighting. All the food buffs earrings and other stuff wont do anything if your fighting something you can't actually get skillups on in the first place.
Very good skill up food. I haven't tried the Maringnas but these have a much more noticeable effect than Saltena/Elshenas. I was able to take Club from 331 to 404 cap in 2 hours 7 mins as WHM/MNK counterstance fighting 3 Mandies at a time in Abyssea - Altepa.
It also helped with ~280 sword up to 334 cap on THF, so I don't believe this is limited to 300+ skills only. I haven't tested it with any skills significantly below 300. No noticeable effect on ~240 Guard skill ups (Saltena/Elshena don't work well either).