First off, I'm talking as a self-confessed I;S player (and also complainer) even though I've benefitted from him far more than I've been burnt by him.
Firstly, when tryign to work out whether he's a problem you can't just think about the card alone but the deck in which he is in and what options that creates. For example, it's all well and good ^ saying that you have cards which can block him by their strength e/g Ronvid, but equally I have both weather options and warriors to decrease that strength. As a resort, and really only a resort, I have Mandrake and Parasite, and Vandemar for Azur's Thunder, and for very big units I can use Morvudd, again only if necessary. My drakkars increase Imleriths strength by 1 per copy I play, and that makes a big difference.
To those saying it's fine because you can run Mandrake and a lock, brilliant; but I also run these cards, so if you lock me I'll unlock myself. If you mandrake me before I've mandraked myself I may be fucked, but that's almost never happened, honestly.
The thing is, you can't play every game with the certainty that Imlerith is coming, and therefore it's been extremely easy for me to bait out removal just by waiting a bit longer before playing Imlerith. Hell, I've even been able to bait out 6 Viper Witchers (including Ointment) by playing a mixture of perceived threats such as Drakkars. I plan for the fact that Imlerith might be removed, and don't worry about it because I've got Renew - it's all part of the gameplan.
At the end of the day, my biggest worry is not drawing either Imlerith of Ge'els in order to get Imlerith, rather than removal my opponent has; I'm hardly the worlds best player, currently grinding at rank 18, but Iv'e still found it relatively easy to bait out my opponents answers to Imlerith. Most of my losses which my Eeredin Imlerith deck have been because I either didn't draw the cards I needed, I played badly, or because I was drunk (and therefore played badly).
The only deck I've really had problems with is NR armour decks.