I haven't seen issues with Search Indexer, though the Anti-Malware Executable thing does seem to spike up at the most inopportune times. (Downloading the latest Windows Updates, actually, when I turned off real-time scanning in Windows Defender, a process it was telling me would take hours to complete suddenly finished in a couple minutes.) But this is usually after I've already terminated the SkyDrive Sync Engine process, so it's probably unrelated.
I have two Windows 8.1 devices that sync with my SkyDrive account. (Side note: I wonder when they'll update this to say "OneDrive" instead?) One is an Asus laptop, and one is a Surface 1 RT tablet. I never have issues on my tablet. I use OneNote on my tablet constantly, and very rarely on my laptop. I do use Word 2013 on my laptop often (and less frequently on my tablet) to edit documents on SkyDrive; but the documents I edit aren't actually in my account, but shared from another account.
Since my tablet is an RT, the executable is likely different (compiled for ARM instead of x86), and I realize the comparison isn't an entirely fair test.