Is this a fair trade in Fantasy Baseball?

No, you shouldn't, you are easily overpaying for Kendrick. Bumgarner turned it around in his last start and he should be solid this year. In terms of marmol, you just don't pay for saves, period. Closer turnaround happens so often, there has already been like 4+ closers that have lost their jobs. Its too early in the season to worry about innings limits. Just bench a starter here and there with tough matchups and you'll be just fine.