The striders give you blaze which helps craft fire arrows. Helpfully, the fuel canister on their back makes a handy target for fire arrows - hit one and the strider will eventually detonate, and often takes out the ones near it with the explosion. They don't always drop blaze, but so far the exchange rate has worked out.
Also, don't forget about the spear and rolling. I managed to put a trap too close to a group of scrappers and watchers and alerted everyone, but managed to take them all down with some rolling and spearing.