When playing a glasscanon
First of all, when you are sniper you are the target. I can't think of any other hero in the game that people like to kill as much as sniper. The reason is easy, you are as tanky and as fast as a guimauve.
So there are simple rules to follow (those apply to any glasscanon) :
- Never (ever) be in front when you push/def/gank etc. You stay in the back, and you watch where the enemy heroes are, then you position yourself accordingly.
- Having an escape mechanism is not necessary but strongly recommended. It can be a Shadowblade (classic) but you can also go with forcestaff or blink dagger. The latters allow you to reposition yourself through the teamfight and Sniper desperately need good positioning. The furthest the better. Plus it allows you to kite melee heroes really easily.
- If you're going glasscanon, always save a spot for BKB because the best item versus glasscanon heroes is a blade mail. Since blademail deals pure damage, you can have your BKB ready for when the blademail is activated so you no longer take reflected damage. I usually build BKB as a 3rd item (boot excluded). Something like Maelstorm > Cristalys > BKB then upgrade into Mjolnir and Daedalus. And if I feel like I need it I get my escape mechanism right after boots.
- Go for easy target. As you said you can 2/3 shots squishy heroes so when a fight start, activate your BKB to avoid normal disables (not Axe's Call) and magic/pure damage and snipe the support really fast, usually the fight is won at that point.
If you feel like you want to tank a little more, consider the following :
- As mentioned above : BKB versus magic burst, disables and blade mail
- Satanic is a viable choice. The active last 3.5 sec while Axe Berserker's call last up to 3.2 sec so you can pretty much tank the whole thing with a satanic. Plus it give strength which upgrade the health of your illusion if you have a Manta Style
- Heart of Tarrasque is situational. Get it versus heroes that deal pure damage. Since pure damage ignores armor, having more raw HP helps a lot. Same as Satanic, your illusion benefit from the HP as well.
When playing versus axe
Axe doesn't have a truly reliable disable so you can pretty much ignore him through the fight. He sole purpose in lategame is usually to get a good initation and finish off the low life targets. Being spread out, having good defensive/offensive wards, having a gem are the only things required to no be bothered anymore. If you can see where he is and if he fails his initation, he will pretty much die for nothing. Axe is what you can call a "one trick pony" hero, blink > call > culling blade. If he can no longer do that, he become pretty much useless. Also Axe relies on snowballing to get more items. Afk farming the jungle is not efficient enough for him to stay there for 20 min so avoid dying in early game (I repeat myself but wards are the key here) and he won't be an issue later at all.