One thing that wasn't touched on, why you build survivability in the first place. Viper does slow damage over time and the longer he's alive, the more damage he does through various means(his orb, his passive that reflects dmg and his passive that does more dmg as people get lower). He does fairly ok damage without any items early/mid and that's why you build tanky first, so he survives and gets to do his slow but steady damage over time, plus mek is a great teamfight item early on and yeah no mana problems. Razor is kinda the same, insane damage over time but needs to survive, has more mana issues but still good item and mana issues go away right after(or before) when you get a point booster for your agh. Incidentally, Viper also does that, meka into agh or sometimes pointbooster meka agh.
As for the jungle, one thing to remember is in dota, not having a jungler doesn't mean your jungle is wasted. Supports stacking constantly and pulling can make use of a good part of the jungle even without someone actively killing shit in there. Everytime you stack a camp, it's the same as having killed it, only delayed(and obviously it can get stolen). Most junglers can't even clear all camps anyway, in fact I don't think any jungler clear all camps until 20mins before they respawn, so a support who stacks a hard camp and double pull the easy+hard camp is basically doing the same job as a full dedicated jungler in terms of using the jungle gold/xp. Granted double pulling on Dire is fucking gay, so that's not as good there, nor is stacking. Fucking dire jungle is shit.
Other thing to remember is besides a few exceptions, you get more gold in lane than you do in the jungle. Exception would be Enigma and potentially Doom not sure. Enigma is the only jungler that clears fast enough that he can actually make good gold/xp out of the jungle early game. If you play Naix, you'll get more farm in a lane than in the jungle, unless the lane is way fucked(like vs an offensive trilane with only one support who's like kotl or some shit). You should only go in the jungle if it benefits your team. It's even worse if you're using the pulls to level on, that hurts your supports for no specific reason, at that point you might as well pick a real jungler or learn to jungle by cutting trees so you only get hit by a single mob in every camp, letting you do hard camps right away.