My opinion of this card has had its ups and downs, swayed by varying factors which include new rulings and blatant ignorance on my part. When I first saw it I thought it sucked. Then I thought it was too powerful. Now I'm somewhere in between.
It went like this: I first saw the spoiler for the card when (if memory serves) minion companies were still only allowed to start at Minas Morgul. At that point, Radagast the Tamer had little to distinguish himself from his Maia compatriots. As a hazard creature he was more playable than Pallando, true, but on the other hand his event ability completely sucked. Alatar's was great offensively, Pallando's was always moderately (if not particularly) useful, and Gandalf and Saruman could be devastating against the right decks. Radagast could be truly troublesome to decks that hang around Mirkwood - but who really hangs around Mirkwood? Sure, you'll probably pass through it from time to time, but when it came down to it, the Tamer seemed, well, tame.
All that changed when it was announced that minion companies could start at Dol Guldur, not least because the result was that (at least around here) practically ALL minion companies started at Dol Guldur. Now, the possibilities of playing Radagast as a hazard creature were greatly enhanced. He would be playable on the first turn in the vast majority of cases, a devasting 2@13 attack. What hazard keyed to Rhudaur can hit wizards that bad? None, of course. I had visions of orc-corpses littered among the trees, victim to this ridiculously powerful creature.
I was forgetting something, of course - something that was pointed out to me in a NetMETW game. Keyed Radagast to Southern Mirkwood, which is a dark domain, means that his attack is detainment, because attacks keyed to dark-domain by type OR BY NAME are by definition detainment attacks. This weakens Radagast considerably. Sure, 2@13 detainment is still pretty annoying, but it's not deadly. And chances are far less that you'll be able to key Radagast elsewhere in Mirkwood. Even if a company is making forays into the dragon-lairs, for example, they can use starter movement and thus avoid having to pass through Heart of Mirkwood by name.
So, in my mind, Radagast fell back down to similar levels of playability as the other Istari. That leaves his event ability, which gains a considerable boost with the starting-at-Dol-Guldur rule. Since most minion companies start at Dol Guldur, and do a fair amount of their trafficking in and around it, it means that Radagast stands a good chance of increasing the hazard limit of a lot of minion companies. And that extra hazard can very often make the difference. YMMV, but I'd say that the chances of a minion company starting at Dol Guldur are a little better than the chances that it's overt, making Radagast and Gandalf both good sideboard cards, but giving Radagast the slight edge.
In my mind, Radagast the Tamer now sits somewhere in the middle - not the best Maia hazard, but certainly not the worst.
Original card review taken from : http://fan.theonering.net/morgulrats/
With the authorization of the webmaster.
The reviewing team consisted of Gwaihir (Chris Farrell), Gimli (Nathan Bruinooge), Ohtar (Charles E. Bouldin, Esq.), Radagast (James Kight), Joshua B. Grace (Beorn), Martijn Steultjens (Fram Frumgarson), Jason Klank (Saruman) and Jeffery Dobberpuhl (Wormtongue)