Seems like I solved the issue. Right after I finished setting my Google/CyanogenMod account and stuff, I immediately switched to ART. Now I did a complete reset and tried to install WhatsApp, this time being successful. Any idea about why ART blocks WApp?
Device: Samsung Galaxy Tab 2 7.0 (Wi-Fi)
CyanogenMod version: 11-20140829-NIGHTLY-p3110
Android version: 4.4.4
Kernel version: 3.0.31-CM-g9b3f943
Build number: cm_p3110-userdebug 4.4.4 KTU84Q dd085ead33 test-keys
Recovery: CWM 220.127.116.11-Swipe