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?
: Samsung Galaxy Tab 2 7.0 (Wi-Fi)
: 3.0.31 (CM-g9b3f943
: cm_p3110-userdebug 4.4.4 KTU84Q 573a9b7bfe test-keys
: CWM 18.104.22.168-Swipe
(Sorry for any grammar errors, English isn't my first language