Zaphid I think SD CAN be good, but most of the time isn't. Mirana arrow combo requires coordination, and it also requires you to be near Mirana(if they go mid or offlane then you're not gonna follow them there, other than maybe roaming for a random gank but if she's offlane, fuck that noise). Disruption is really good lategame to save your carry but again it requires coordination. Other than that his fight contribution is low, purge is nice to prevent people from running and shadow poison is nice to scout and turtle, but in a teamfight they both do very little. Soul Catcher is an insane spell but getting it on the right person in the middle of a teamfight is close to impossible and disruption has so many uses you can only pick it for one thing and overall, you won't do all that much if your team isn't very good. I just don't like him much, I like his concept and I like his skills and he's a strong hero, but in pubs he's the kind of hero I don't want to be playing. A worse example is Wisp. Fucking insane hero, but I'm never picking wisp in a pub ever(plus since I don't play him I'd be a shitty wisp too so that doesn't help). At higher ranks of pubs picking competitively good heroes can work better as people expect and are expected to know what the fuck is going on, but I'd say 4000 and under, you definitely don't want to be relying on shit.
On the Lina thing, I think she does ok without a real setup. Yes it takes some cancelling and yes sometimes you'll miss but often while you don't actually land the stun, you force the guy to move in a weird direction and stop doing whatever he's doing to do that instead, which acts like some sort of stun(or confusion debuff). There's plenty of times where you can lead someone into a situation where they simply cannot dodge it to. She provides quite a lot though, even if you miss the stun, especially with the value point in her passive. But more importantly in teamfights, you rarely miss the stun, and Laguna Blade is a big deal(if you're remotely farmed), that's why I like her. Also once in a while you'll get early game kills and you kinda snowball into a massive beast with like blink agh malestrom in 30mins and shit's way fun.
Anyway plenty of supports you can do well and have an impact on the game. Have to play in that mindset though, you do want to buy the wards and the courier(and upgrade it, fuck god people who don't upgrade couriers are such dicks) but you want to be farming, you want to get levels and you want to get gold. If your carry is one of these assholes who don't buy TPs, fucking TP to the lane that's pushing and farm that shit, even if he's waddling his fat lazy ass over there. Stack the jungle and farm that shit even if it means going back to base to get mana after(obviously need to read the game a bit, bad idea to do that when enemy is grouping up to push). Pubs tend to be slower paced than pro games, there's a lot more room and time for supports to farm up, and it's a lot less likely peple will be able to carry a lvl 8 support 30mins in.
