no offense to your friend devious, but hes not what i call a "good" druid. the core of druid pvp is that you cant outfox the fox, which is a neat way of saying you cant beat a class at its own game (or at least you shouldnt be able to beat a class at its own game, which is mostly true in WoW). in other words, a boomkin shouldnt ever beat a mage in a straight nuke fest, a cat druid should never beat a rogue or warrior in a straight melee fight (without using bear) and a resto druid shouldnt be able to just outlast other heals (in a straight outlasting fight).
in order to beat another class as a druid, you play your strengths vs that class's weaknesses. thats kinda hard (or near impossible) to do at times, such as a feral trying to beat a warrior using nukes, but it applies to less direct means, such as (in the case of feral vs warrior) proper usage of forms and outlasting. most feral druids ive seen who fight warriors use a very warrior-like mentality, which is to say they get in the fight and they stay in the fight. rarely do i see a druid try to cyclone or root the warrior, get some distance, heal, drop combat, restealth, and jump on the warrior again (a technique that effectively ends it for the warrior).
of all the classes in game, druids of all specs have the best chances of beating any other class. spec alters the general level of success vs a class (resto and feral do better vs mages than boomkin for instance) but overall a druid that knows what s/he is doing has at least a better chance of beating most classes than those classes have of beating the druid.