Hi there. I am reletively new to this forum and warhammer in general. Me and my brother started playing just over a year ago and the majority of my battles are between his highelves and my WoC. I just want to add that i love chosen and try to use them as much as i can so i thought i would put my two cents in. The unit i have the most trouble with killing is tbe white lions. Against high elves the chosen have the ability to, with the I roll, strike before white lions. Now if the white lions unit is on the smaller side 21-28 and 7 wide i find the ability to hit the white lions before they hit my chosen is key. When using the halberd nurgle or ahw khorne builds you can usually take out enough to reduce the attacks you recieve back. Keep in mind that points wise it is not a good match up but i find that when im up against a strong unit of WL especially with the banner of the world dragon i will throw whatever i can into killing that unit. Against larger units taking different buffs can be useful to increase the survivability of the chosen because the more times you hit white lions the less striking power they have. I love the versatility that chosen provide and although they are expensive i find them very useful if i can afford to field them.
Lionstars with the BotWD are a headache but also a sizeable point sink for your adversary... but that said so are chosen, especially if you factor in the warshrine and the numbers needed to make them a threat. If throwing dogs at the Lions isn't an option while you deal with the rest of his troops then the combo-charge is the way to go.
as you already mentioned MoN and Halberd are IMHO the best solution... Halberds make for reliable wounds while Nurgle gives you some insurance vs return attacks. That said since the Lions have a good Ld and are stubborn you will probably need to destroy them to an elf... risky proposition since you are relying on rolling well on bound spells/EoTG table. As such I'd suggest a couple of Flank charges by chariots... elves love those impact hits!
I have to agree with you that the nurgle chosen's staying power makes them the best choice. In eigth edition (and especially against stubborn opponents) sticking around and grinding through the foe is what its all about. One of the reasons i like the khorne unit is that i can keep them cheap because all i really need from them is the front rank to get there full attacks in. With the ability to get +1 S,I,or, A combined with throwing 4 dice at the roll from the warshrine i find usually you can get what you want. And for the times you dont well they are still a powerful unit. Chaos is fickle or whatever the book always says lol. Though I agree that throwing dogs at them and killing the rest of the army is the best way to fight the lions; what can I say I love to kill me some elves. The last thing i would like to add is that i dont agree when people say the cost of adding a warshrine makes the chosen too expensive. I find the warshrine to be a very cheap pseudo tarpit (something we dont really have a lot of access to)type of unit and for its price to have a 3+ ward with the mark of tz makes it worth having around all the time. The added bonus of giving your lord an extra T or saving your bsb from spawndom combined woth how great model looks makes it one of my favourite units. I hope i didnt ramble too much and thanks for the response!