It seems to me that people are looking for a single card to deal with multiple welders. Engineered Plague serves this purpose well.
Most decks with welders run Red, Blue, and Black, none of which can easily deal with an enchantment. Control Slaver seems to be in the best shape, with the most counters and Cunning Wish into Chain of Vapor. The Tog mirror match seems to be the only place that a maindeck Engineered Plague would be completely useless.
The main thing that I like about the Plague is that it dodges most of the hate: no REB or BEB, no Rack and Ruin. It also kills critters as a state-based effect, which stop a certain class of pumping creatures, such as Quirion Dryad, Nantuko Shade, and Basking Rootwalla, and prevents your opponents from playing suseptible critters until the Plague is dealt with.
MATCHUPS
Slaver - Keeps welders (or pentavite tokens

) off the board. Hard for them to deal with a resolved Plague.
Keeper - Forces them to make angels or deal with the Plague
Grow-A-Tog - Keeps future Dryads off the table. Since dryad costs less, not too good.
O-Stompy - Uhh ... keeps lizards off the table? Not too good.
Dragon, Storm, Draw7 - It's RAID!!! *Poof*. Too slow though. Completely worthless main unless they run main deck Xantid Swarms.
FCG - Doesn't stop the key triggered abilities, but nukes about 1/3 of their deck. A second one nukes their entire deck.
Fish - Always a good target around
Is the Plague strong enough to put in the main deck of Tog (or any deck playing black) for a large tournament? What about the sideboard?