Yes it is still very much an issue.
I'll reiterate what I've said before, lest I be misunderstood as meaning that Vikings should be even harder to play or made ahistoric, that I don't in the least mind that they're an unholy menace, because they were. Nor should I be able to round up my entire army and send them off to the other end of Europe, leaving my realm bare and naked and NOT expect to be punished for it. I should be. Severely. Just as I should, and will, be punished when I raise everything and go to war against somebody on one side of my realm. Everybody who's been waiting for a chance to attack me will pick that moment as well they should. It's what I do myself when I'm trying to find a good time to attack/declare independence etc., so it'd be silly for me to even want for the AI to not have that.
My issues with "defending against the heathens" are these:
1) I hate micromanagement and mindless clickfests. I would happily accept as perfectly reasonable and historic if I could just assign a "defense force" with some leaders and put them in charge of defending the realm while I'm gone. If they do a less than optimal job of it, they're AIs after all, then so be it. But at least I don't have to raise-attack-disband every three minutes while being busy on the other end of the map. Yes, I should pay a price for keeping my homeland safe, definitely, but that price shouldn't be enjoyment of an otherwise excellent game.
Some may enjoy spending 2 hours clicking around the map, and more power to them. They'd still have the option and they'd most certainly do better by doing everything themselves. That, too, is fair. If you want it done right, do it yourself. I just don't want to be forced to do it too. It's the only thing that detracts from playing from my favorite starting point: the British Isles at the CM or ToG start. You can't go anywhere once you're England unless you enjoy clicking yourself into stark raving madness. I'd LOVE to occasionally go help out my Lombard ally, but not if it means that I have to play "LevyCraft" for two hours until my mouse begs for mercy.
I've found ways to alleviate it somewhat. a) Create Duchies on coastal areas. Just make sure that the Duke has more than one county of his de Jure because the AI is an idiot. If the Vikings land 200 men on his primary county where he has 900 levies, he'll just sit inside his castle and watch his crops burn and his peasants get raped. RAISE THE DAMN LEVY, YOU IMBECILE! Of course, that may be because of the incomprehensible to me game mechanic under which your vassals raise levies with 0 morale who then have to sit around and hold hands and sing songs for a month or two before they're able to fight, whereas your own demesne levies raise themselves at 100%
b) park your retinue on the coasts. It's costly, but it's fair. Again, it shouldn't be CHEAP to fight off the barbaroi. Unfortunately, you have to have a decent realm before you can build one that's big enough for this duty, and it sort of turns your "elite personal troops" into patrol cops. But hey, as long as it works. Not optimal, but every little bit helps. Just heaven help you if you're Lombardy or England with a realm that's almost all coastline.
2) Why on earth can't I punish those horrid horned heathens? They land on my shores, burn my crops, rape my nuns, burn down my churches, steal my gold and kill my peasants, but there's not a damn thing I can do to them because I "don't have a valid Casus Belli?????" What? Avenging the burning, raping, mutilation and killing of 10,000 of your people doesn't make for a "Casus Belli?" Oh no. If I want to give them some Christian payback, I have to first park my chancellor on their territory for a couple of reigns (they sure do take their time fabricating claims, don't they?), then pay an exorbitant price for the document giving me a legit reason to attack the bastard who just burned down a county of mine, raped my wife and bashed my childrens' brains in on a portcullis, and THEN I can go kick their furry arses. After THAT, once I'm neighboring them, I can holy war until my face turns blue and you better believe that I have, but not until then.
Invite a guy whose mother's brother's cousin's grandfather once ruled over Whogivesafart to court, land him and then you have a reason to invade and take somebody's lands, but watch a generation's worth of innocents, including your own family, get slaughtered by heathens that the church cared not one bit about? Nope. Attacking THEM would be simply going too far!
And what if they (or, for that matter, anybody else) take a holding and capture my children? Can I go attack them back, siege down every one of their holdings and get my kids back? Nope. They must be hiding them in the forest or something. Heck, I could live with it even if they decided to behead my family just to spite me right before they lost, but I can literally take every inch of land they hold, every castle, church and city, wipe out every last man of their armies, capture every member of their dynasty, but I still can't have my abducted kids back without paying a ransom. Seriously????
That's why I pretty much never ransom Vikings anymore. I enjoy executing them too much. That's just about the only thing that the game will allow me to do to pay them back. Not that they care. They'll have another 1,000 raiders raised tomorrow in their Viking Bacta Tanks.