Remy isn't unproven in the league and most importantly, his style of scoring is being pacey and latching on to through balls, not a great footballer but an excellent finisher. With Fabregas behind him I wouldn't be worried about that combination working if Costa was out, without Remy, with Torres's form and a likely not great if played every game Drogba I would think losing Costa would be a huge loss, with someone like Remy and Fabregas to supply him, I don't think they'll have any problems.
In terms of City being best team on paper, I can't agree. Silva/Nasri are so poor in so many games. Liverpool were poor in the second half, the first half it was City's lack of any pace at all down the wings that hurt them, they didn't get those two involved and literally in dozens of games in the past 2-3 years those two have been the weak link against certain teams. Where the midfield sits deeper and/or Yaya is having one of his pretty frequent lazy games, they struggle to get support forward or counter attack with numbers. Navas has that pace, not the quality and is a bit injury prone.
City have wings, central mids, defensive mids, strikers all covered, fitter/stronger CB's as it stands(will see of Mangala changes that and if Kompany can stay fit).
Fernando/Fernandinho don't look anywhere near as good as matic defensively or offensively. Matic frequently gets involved in counter attacks and offers real quality when he does, and goals. Yaya, power, some great finishing, but he's sporadic, has frequent lazy games and isn't particularly strong defensively. When he's at his peak he's brilliant but I don't think I've seen more than 2 or 3 games in the past 5 years he's been good for even 60 minutes of a game, he's often a peripheral player but with bursts of brilliance. Their central midfield isn't as dominating or consistent as Chelsea's and winger wise, Chelsea have all kinds of options, defensive options, pacey options, attacking options, ultra attacking options.
For me at this point Chelsea have a noticeably stronger team on paper than City. City need to buy some genuinely pacey wingers and then need someone more reliable than Yaya. If/when Yaya is injured they have absolutely no one remotely close to his quality in a creative or goalscoring sense.
The one real weakness that Chelsea team has now, is Mourinho. They really should have won the title last year but went to Utd/Arsenal looking for a point, playing too within themselves, got lucky against other teams like Liverpool when they went looking for a draw. That mentality hurts the team in general. If he continues giving up points in tough fixtures it's not because the team aren't capable of getting them but because Mourinho has a weird mentality about those games.