Really depends on the God. For Athena more tank is almost always better then some more damage in arena. The only exception is if your team is so bad they can't deal damage. Doesn't matter if you can solo zone some guy out at 50% their hp if you die when you manage to taunt 3 people. For conq sure maybe better to be able to zone one out by yourself, I have almost no games as athena in conq so I can't say.
Also Athena is not the best aura bot, as she engages the enemy team pretty much alone most often (atleast in arena), all those auras do not benefit the team. Better as I said with pesti, void stone etc. Key to aura botting is knowing where you will most often be in the fights. Kehp for example does aura botting really well.
As for playing aura bot I do this frequently, the key is mixing it up so you can support with it apart from just mitigating and body blocking. Gem of iso for example. Or when I play Geb/Kehp I build a chronos pendant almost every time. Spear of magus is also a favorite for me on kehp. I can have 3 def auras going and just build spear so that my mages do way more damage. Its like 50% more damage on their squish if they have someone with HW close by. So one item can add 50% dmg to my mage, pushing them from like 20k dmg to 30k dmg over a game done right. What is more useful? Building the kehp for dmg and go from 15k to like 25k while providing way less defense for team or just build items that increase your teams dps? In arena where 2 mage is frequent adding 50% dmg to both or dealing 50% more dmg yourself, it is an ez choice.
For Ymir his base dmg so high a void stone and a deso is all that is needed to carry good dmg through all the game. But some games getting that extra deso item actually punishes you more then it helps. Rest you can aura up and winged blade ofc.
Most often though one single aura def item is enough either sov or HW depening on what dmg they have that you need to mitigate for team. Personally I do not like the 10/10 aura item at all. I rather get gaia+mantle later. In some rare cases you need to mitigate both dmg types with auras. Witchblade is super good as well, some games. And some games all 3 are good to have. For example witchblade heavily impacts what an Au kuang wants to do in arena, add HW on that and he needs to counter build so hard you heavily impact his game. IF they also have a merc, that relies on AS and a herc+ho yi. that is a lot of phys aoe dmg that is pretty much impossible to stop going on your team and the only way to try mitigate it is building sover. I mean good luck "zoning out" this team with dmg, merc can ult through whole team without commit, herc can boulder without commit, ho yi can ult without commit. To not aura bot that game to avoid all team dying or all your team zoned out from a merc+herc ult is way better then you being able to zone out their hunter.
Yesterday I played Anubis in arena. We had a baccus tank and they are often jumping into enemy team and I felt we needed another stable backliner that could peel and mitigate their zeus+cerb combo that is a lot of mag dmg that is hard to avoid. So I got HW first item, let our awilix and baccus combo do the main carry work and made it my job to keep our hel and medusa alive as a 2nd off tank. I got HW first item, then normal build with spear of magus for pen so hel and baccus could do more dmg. It worked excellent and we won. Late game I couldn't tank at all but early and mid we won almost every team fight cause their team couldn't put out enough dmg. What they needed was spear of magus on either cerb or zeus but they didn't get it. The feeling you get when someone get zeus combo on them and you just walk in and take 2 of the bounces from the shield and mitigate it with HW and your teammate runs away with 20% =)
Yes and its more difficult in conq then in arena. I would say with experience you will know better. Keep eye on map, try get a feel for CDs, check ult timers etc before committing. And if you jungle sure start with some dmg items so you can farm, void stone maybe (does it still apply to creeps?) But if your team is derp, with squish support and squish solo you must build quite tanky mid and late game to have a functioning team.I think the most difficult thing on athena is, and thats something I am still struggling with, is to coordinate the taunt with your teammates. Say you get a good taunt off but your scylla isn't ready or you see the scylla in ult and low health enemies nearby but your taunt is still on CD.