I find them really hit or miss and I have no idea what exactly makes me feel that way. I really like Mrs God and Rise and Fall but strongly dislike Can Do It and Secret Alibi, for example. I definitely agree that Deris' voice is better suited to heavier material though.
New Blind Guardian has also grown on me. At first I was a bit underwhelmed, but the first and last songs kick arse, the massive choruses in both are great. The other songs are mostly quite good too. Probably the same level as the ANATO stuff (excluding And Then There Was Silence, because that song's better than almost everything). But overall way better than ATITM. I really like the first ballad Curse My Name, but not such a fan of the second, War of Thrones.