as powerful as goro goro is, I think that the strongest logia to date is pika pika. the user becomes the fastest thing that exists, fast enough that gear second luffy is "slow," and gains tremendous destructive power. during the marineford war for example kizaru made a big star that shot dozens of little laser blasts to destroy ships. while other logia have similar destructive potential, most of them require the user to use a facet of their body as part of the attack, such as sakazuki using magma fists. pika pika has long-range capabilities that are almost unmatched as a result. in close-combat, pika+kenbunshoku makes you untouchable because you have the fastest possible reaction time and can see hits before they land. kizaru has also demonstrated that pika pika allows the user to become weightless and levitate, a power few other logia demonstrate. a pika pika user can also seemingly make weapons out of light to fight against haki users, as evidenced in borsolino vs rayleigh. I also think goro goro seems stronger than it is to us as an audience because when enel was encountered the strawhats did not yet possess the tools to fight him whereas he was in his ideal location and had been preparing for years to destroy skypeia.
for zoans, I think that marco's fruit is not only the strongest zoan but the strongest fruit. while in full phoenix mode, marco seems to be virtually indestructible like logia, but can also use his blue flames to heal from damage he accrues while not transformed. flight is also nothing to sneeze at. while the buddha fruit is strong, just like gura gura all it really has going for it is pure destructive power.
for paramecia, I would say it's a toss-up between ope ope for the reasons you listed, kage kage, and doflamingo's fruit. kage kage's place-switching teleport is more than enough to qualify it for top tier, but fighting someone in the sunlight means that you can instantly kill them if you can cut their shadow away. merging with your own shadow is also a possibility, magnifying your own strength. the zombies are just one facet of one of OP's most versatile powers. doflamingo's fruit is also crazy broken because of the string double ability and puppeteering, neither of which seem to be vulnerable to the ubiquitous haki. dofla's strings can also be imbued with haki and are virtually impossible to detect until they've cut you up and, as I mentioned in my picks for zoan and logia, the string fruit lets you fly/travel by air. introducing a third dimension to combat makes it much more difficult for earth-bound opponents, such as EVERY STRAWHAT and 90% of the enemies encountered, to even hit you, much less defeat you.