Nerfing is not a good game design practice. It is basicially linearly increase and decrease some numbers, be it damage output or defense strength. A better practice should be make every template has weakness so that one is not invulnerable any given time. It is like the rock-paper-scissor kind of play. Just make more sophisticated than that. One example, a bard used to be a bane to tamers with their discording and peacing. A template should not be able to stand against every other templates. I am sure we will come up with great ideas on how to weave the web.