swim run good bike bad

so i have been doing tris now about a year. i put it 3 hours of swimming a week, 10 hours of biking a week, and just 3 hours of running a week. However, i can see my swimming and running improve every month. For all 3 sports, i do intervals, long training sessions, and hill climbs if applicable, but my biking is still weak even though i put it in the most time each week. I know if i had a power meter i can track my results a lot better but i don't have one. I just need advice on how to improve my bike performance with the allotted 10 hours i have to train for the bike.