I dunno if I like the deal either Moe, but I think you're selling it short. I agree, Span looks pretty "meh." He's always had a decent EYE, but certainly not this good. If the contact skills have slipped then maybe he's weaponized the EYE to cover, but that obviously can't be sustainable. However, it could work for a decent amount of *this* season, which is all we really care about anyway.
Strategically speaking, we did need another outfielder. Why, when you have Haniger/Heredia/Gamel/*Gordon? Because the playoffs exist, and are clearly our goal this year. Dee will need to play second then, and we'll need outfield depth in his absence. Gamel is a question mark, Heredia could be overperforming, Andreoli has been a ~.780 OPS bat in AAA and is probably a .700 in the majors if he sticks at all. We keep taking draws at the 3 to make 2 deck in LF and CF (see Suzuki, Ichiro), and this one is likely to stick. Also injuries. Never expect the Mariners to stay healthy.
Really though, the main point that you're overlooking by giving him nothing more than a throwaway line at the end is that Alex Colome is GOOD. This is their CLOSER, you realize. All Star in 2016, led the league in saves last year, 84 saves the last two years combined. His ERA is bad this year (well, its at 4.15) but you know what isn't? His FIP, still down at 2.69, LOWER than either of his previous seasons. His Ks (9.6) and BBs (3.3) are still at career norms: the only problem is his BABIP shot up to .354 after sitting at .280 the last two years. Moreover, the regression has already begun: in his last 17 appearances, opponents are hitting .194 and his ERA is 2.14. Bottom line, this man is instantly our second best reliever, and probably by a decent margin. He's a legit closer, or a Yankees level setup man. That bumps Nicasio out of the role, and allows for an eventual hot bullpen of Sugar/Colome/Cook/Pazos/Altavilla/Nicasio* throwing flames down the stretch.
So yeah, losing Andrew Moore hurts. I didn't like him nearly as much as some of y'all did, but he had his strengths and he was one of our best remaining pitching prospects. BUT. We turned him into a useful outfielder with a highly consistent track record, and another team's Closer who we have under control through 2020. The way I see it, we paid a medium price for some much needed OF depth, and a massive bullpen upgrade which we get before the feeding frenzy of the trade deadline. Seems like a reasonable deal to me.