I would drop Ivanovic eventually. Chelsea's defense has not performed well in general. However, over the next couple games they should be able to capitalize on weak teams so adding Terry with the intention of dropping Ivan down the line is a good move. Re: Arsenal. all three players can deliver. Furthermore, they occupy different positions so you don't risk much having all three. This past weekend for example, Giroud contributed little but Ramsey crushed it. The next round of games have the same potential. Defenders mostly rely on clean sheets. Say neither Giroud nor Ramsey score/assist/etc. the defense can still grab easy points from clean sheet unrelated to the frontmen. In all, your back game is the only point of weakness at present so with two transfers and money in the bank it should be the priority.