"From whence" is fine. Idiomatic English has many mild tautologies: reason why, time when, man who.... (Oliver Kamm of the Times)
But don't telegraph your punches. Take people by surprise. Avoid starting a sentence with “Alas...” – you haven’t told the reader what's sad yet. Same goes for “the devastating war that killed four out of six of the country’s youth”. The stats tell the story.
"A graduated hierarchy of measures, what does that mean?" (BBC Breakfast Most hierarchies are graduated.)
All you remember is the horrible colonial past. (Speaker on Sunday Morning Live about the Kohinoor, the Elgin Marbles etc. It’s like saying “By the way, colonialism was wrong”.)
Don’t go too overboard. (Once you’re overboard, you’re overboard.)
frozen in formaldehyde (Many hits on Google. You preserve specimens in formaldehyde at room temperature, or put them in the freezer.)
In an age when the tip of the devastating iceberg that is sexual assault in the military is only beginning to emerge... (brainpickings.org It's the sexual assaults that are devastating, not the metaphorical iceberg.)
insulated ivory tower
It’s a mundane world. (What would you expect from the mundus?)
light-winged dryad of the trees (Keats Dryads are wood nymphs.)
MGM is closing after amassing crippling debts of more than $4bn. (That level of debt is obviously crippling, there’s no need to say so. Either “crippling debts” or “debts of more than $4bn”.)
Purple tomatoes that could help to slow the ravages of ageing still alive today. (slow ageing – it's like talking about the plague/spectre/scourge of something you don't like)
The caterpillar absorbs poisonous toxins from the vine, and secretes them onto its spines. (Life on Fire, Eden. All toxins are poisonous, and all poisons are toxic.)
The parks are bursting full of exotic flowers. (Saturday Kitchen full of, bursting with)
The virus, which scientists first discovered in Britain a month ago… (Times 2012 Did they discover it a second time somewhere else? How can you discover something twice? Or was it the first time it’s been spotted in Britain?)
This defeat shortly paved the way for the devastating Abbasid sack of Amorion, one of Byzantium's main cities. (@JamesThorne2 There is no kind way of sacking a city.)
World War I “completely upended the old world order”.
More here, and links to the rest.