Funny, I've got a Vendetta and I love it, and it certainly plays better than the Schecter Blackjack I tried while shopping for such a guitar. I also tried a LTD Viper (what was before the 400 series? 300? 350? Damn I'm old) which seriously did nothing for me. I think it's somewhat unfair to compare your ESP Horizon with a Vendetta 4 when pricewise it's closer to the MH250. The Ibanez that you purchased must surely have been more expensive too?
USA Deans certainly can't be accused of being overpriced (OK, maybe the USA Razorbacks, but hey, that's signatures for you), as they're available for sub Les Paul money with PRS+ quality. You can even get customs for the price of a PRS "artist" upgrade.
The Japanese Hardtail pros they did last year are awesome bang-for-buck if you can still find them.
The most divisive thing with Deans is the neck profile, if you can't get on with it, you're not going to like them, but some people don't like thin Us either.
I would say, owning one and having played other Deans in the £300-£400 range, they're right at the top of the pile in terms of build quality for that section of the market.