Gonna hit a few points covered across this thread:
1. Trump ain't nothing to worry about for the Ds. His unfavorables are absurd with most of the population. He turns lean right voters into hard left votes, hence why HRC beats him in a recent poll done in Kentucky. Fucking KENTUCKY. He gets the extreme right fringe out in droves though, and the Tea Party has turned that into the dominant force in the primaries.
2. Sanders is not Obama. Hell, Obama isn't/wasn't Obama. He was a valid candidate to be sure who got early traction with a strong showing in Iowa, but what really did Clinton (and McCain) in was that Obama's campaign was literally a decade ahead of the field in utilizing social media to rally voters, organize voting pools and, most importantly, extract funding. His outreach machine was unprecedented across the globe. It is now effectively being rolled over to HRC, I'm sure as some sort of horsetrading for Bill Clinton's ardent public support and campaigning last election.
3. Where did this "Hillary has no personality" bullshit come from? She has always been a unique, charismatic individual. She's a damn good interview, whether that is on the Daily Show/Colbert where it's superficial politics and jokes or in a hard hitting political wonk session with the more "serious" journalists. Her campaign is going to get about a year of negative/attack ad free play before the general to mend her negatives that do not stem from a lack of personality, they stem from the fact that when it comes to politics she's a cold, calculating, strategist who knows what she is doing 99% of the time. Basically, she's the HBIC but nobody actually likes the HBIC, they just respect the game. They'll soften that image before any rich white guy from the GOP starts lobbing grenades at her, and then much of it will look like angry white man syndrome run amok.
4. The best strategy the GOP has is Kasich/Rubio as POTUS/VP. The other way doesn't work because Rubio is still wet behind the ears and made a flat out statement last night that HRC's resume trounces the GOP field. Kasich has governor credentials, is moderate enough to not alienate the massive middle swath of voters, and would pull Ohio red. Rubio helps with hispanics and pulls Florida their way as well. That is the GOP ticket with a chance, but it's looking more and more like Kasich is going to get slapped down by the John Huntsman Effect (i.e. moderates and lefties consider him pallet-able, so GOP primary voters just assume he's awful).
5. People seriously under-estimate the "first woman president" pull HRC is going to get, or the bounce she'll see from older democrats who secretly didn't want to pull the lever for a black guy with a weird name. If you think black voter turnout is going to decline shortly after cops have been murdering black kids in the streets of most major metropolitan areas while the GOP claps from the sidelines you're fucking high.
Everything is queued up, HRC and Bill are too damn good on the big stage and this time she's running effectively unopposed. They didn't see the coming of social media as a major political force. Obama and Axelrod did. That is the one time they've ever been tripped up. You're talking about a couple who took Jeb's daddy's job when he was the sitting POTUS on the heels of St. Ronnie and actually had the country headed on a decent enough path. They live for that Red v. Blue chess match.