Sturridge and Coutinho are the standout signings, yeah, but I think you're being to harsh on several of the others.
Borini - Not good enough.
Assaidi - Sold for a profit.
Manquillo - Loan - Better than Johnson, cheaper than Johnson... That's alright.
Sahin - Loan - Irrelevant.
Cissokho - Loan signing as LB cover while Enrique was out - Irrelevant.
Moses - Loan signing to add depth - Irrelevant.
Alberto/Ilori/Yesil - One for the future, maybe. We've not seen enough of him to write him off, or to say he's the next big thing, but could be decent.
Origi - Has looked decent at times for Lille this season (7 goals in 26 (with lots of sub appearances) for a 19 year old isn't bad) - Will be a better third choice striker than what we've already got.
Aspas - Yeah, not find of that signing at all.
Lambert - Decent 4th choice striker for the money we paid, but we've already got plenty of those, so a tad bizarre. Still, not fussed.
Lovren - You'd be hard pressed to find many people who didn't think this was a good deal. Nev & Carragher were talking about him being one of the best CB's in the league last season, and I thought he'd do well here. He's only 25, so there's still time, but he does need to improve.
Balotelli - In hindsight, rather Balotelli than Falcao, to be honest. He cost us less to buy than Falcao did to own, and probably added comparatively more to our merchandising, too. Crap on the pitch, but we'll still make most of our money back on him.
Can - Can is a CDM playing at CB because our first choice backline is doing pretty poorly right now. He's looked one of our best players for large portions of the season, and for €8m, I think we've got ourselves a good little player. He'll do well when playing in his natural position ahead of a decent front line.
Sakho - Decent, but he needs to work on his ball playing ability. I'd take him over a couple of the top four CBs as a defender, to be honest.
Lallana - Good signing, but £5m or so overpriced due to his sell-on clause, captain status, and English international status. Was one of my fave non-'pool players in 13/14, and I think if he stays here for 4-5 years, he'll be worth the money.
Markovic - We've seen flashes, but I've not seen enough to convince me we wouldn't have been better off sticking £20m on a striker and promoting Ibe to the first team a bit faster.
Mignolet - He's had his shocking moments, but for £8m (not £15m), I think we've got a decent keeper. His form since the turn of the year has been fantastic, and there's still time for him to improve.
Moreno - Either looks like a world beater or a junior. He's had enough time to adapt to the league, but there's still plenty of work he needs to do to improve. Again, he's only a kid, so time will tell.
Allen - Nothing special, but worth the money.
Objectively, I'd say the only three signings that have already failed beyond reprieve are Borini (from which we'll recoup most of our investment), Aspas (same again), and Balotelli. The rest I'm either moderately happy with, or expect them to come good in the long term.