I think it is fair to say that we miss them both. I agree completely with what you say about our lack of ability to get the ball into the final third, and to control games. Today, that was certainly the main problem, especially in the firsty half. We even struggled to get out of our defensive final third. We tried to play our way out at the back, but there was just nothing on. To be fair, Wigan did well at making at it difficult for us. Their three attackers put pressure on us high up the pitch and didn't allow our defenders and deep midfielder time on the ball to turn and face Wigan's goal. Something that led to many passes back to Fridel. However, when we did have some time on the ball at the back, there was simply nothing happening in front of the ball. There was no pass on. So the ball went back to Friedel again. We seem completely clueless when we have to control play at home. That has been the case in most hoem games this season. Lacking a playmaker of Modric's caliber is part of the reason, I am sure, but I also wonder what we actually aim to do when we build our attacks. Harry got criticized at times for lacking a plan in similar types of games, but things have certainly not improved so far with AVB. At the moment we are a decent counter-attacking team with the pace of Lennon and Bale, and Defoe's movement when he does have space, but we are completely incapable of controlling a game ourselves. That is obviously why we have done better away from home so far.
I do think we also miss some creativity and invention in the final third though that Rafa often provided. Dempsey doesn't have it, end of story, and Sigurdsson is a nervous wreck at the moment. He does have decent vision and a decent pass on him when on form, but right now he is hiding in games. Rafa was always a player who showed for the ball, who wanted to make things happen. Dempsey and Sigurdsson doesn't, and obviously don't have the same abilities either. Rafa got criticised at times for dropping too deep, but at least there was something happening around him, he was more dynamic in his play. Rafa could also receive the ball in a tight spot, and with a good first touch he'd get out of there with the ball at his feet. Dempsey and Sigurdsson don't have the same ability due to inferiour technique and also slower feet.
We also miss the more mental abilties of Modric and Rafa. We lack their experience, and confidence and leadership. By leadership I don't mean running around pointing and shouting, but taking charge of the game, wanting to make something happen. Who will do that in our team at the moment? Who will show for the ball, and take responsibilty for creating something? Especially when things aren't running as smootly as we would have liked? There is no one really. Not in the middle of the park at least. We have wingers who can create something, but they rely on support from elsewhere most of the time. They can't take charge of a game like players playing in a central position can. This is also a huge problem for us right now the way I see it.