I was fed as balls and with kill xp + never backing without tp, I got a huge xp lead pretty quickly. Taric was under leveled but I was also a few levels ahead of my own team.
If you look at the levels, ashe is the same level as our sivir, so it was more taric not being in xp range for whatever reason, probs DC or dead.
I was 5/0 with ~40 cs up on everyone else in the game, so I also had a huge gold lead and in effect more stats.
Edit: people often underestimate the value of Singed ult as well. The stats it gives are worth a load of gold. As a consequence, people don't realize how strong a Singed is with his ult up, even when behind in gold.
Singed ult is worth approximately:
Rank 1: 5976.25 gold
Rank 2: 8537.5 gold
Rank 3: 11098.75 gold
Tl;dr Singed ult gives a stuffton of stats that people don't realize, but looking at the gold value of those stats puts it in perspective.