Unlike with many other tanks, on a well-built Rad/* there's not a huge upside to Cardiac (IMHO); this really unlocks other potential Alpha Incarnate powers like Musculature for even more damage.
Welcome home!
It was such a HUGE relief when I first logged back in (the implications of which are between me and my therapist).
Go...hunt...kil Skuls.
I have two fully kitted-out Rad/BA tankers, and they are VERY powerful; also have a BA/Rad Brute who cycles the Rad tier-9 and with Rune of Protection (Sorcery pool) to achieve tanker level resists.
One observation is that putting the +recharge proc into the two 360-deg attacks is more than enough if you want to save some slots for something else.
Beware of severe End drain issues pairing Axe/Shield, as both are capable of draining your reservoir by themselves... when paired they can suck you dry in one power rotation.
I was able to make a pretty cool (and tough!) ice-themed tank using recolored Stone Armor/Ice Melee.
Stone is now a fantastic armor set, and the fact that Mud Pots has an integral slow effect makes it fit in that way with the ice theme.
I have a 50 Bio/SS tank named "Rikti Hunter K'rang" that absolutely wrecks face; his theme is an alien hunter arrived on Earth following the Rikti invasion, who stayed to help defend Paragon City. 😁👍