What I've read is Watson has improved from non-existent to serviceable as a blocker. But he's not a complete, consistent TE. If he was, he wouldn't be in Clevelend. And $4M is a lot of iron for anything less than a complete, #1 TE. Yes, he can stretch the field, but so can Nelson. I'm just not buying Watson as a good investment for that kind of money. As impressive he always looked against us (bad defenses), he was invisible at times.
And don't think the Bills are done with just one OT. They need depth at tackle. And they need depth inside in case Wood is slow to heal and in case we need an upgrade over Hangartner. I think there's a lot of work to do and a 2nd WR/TE should be FAAARRRRR down the list of priorities.